{"id":78826,"date":"2026-09-10T02:16:17","date_gmt":"2026-09-10T02:16:17","guid":{"rendered":"http:\/\/bangla.sitestree.com\/?p=78826"},"modified":"2026-09-10T02:16:19","modified_gmt":"2026-09-10T02:16:19","slug":"network-devices-vlans-subnets-layer-2-and-layer-3-switches-and-routers","status":"publish","type":"post","link":"http:\/\/bangla.sitestree.com\/?p=78826","title":{"rendered":"Network Devices, VLANs, Subnets, Layer 2 and Layer 3 Switches, and Routers"},"content":{"rendered":"\n<h5 class=\"wp-block-heading\">Network Devices, VLANs, Subnets, Layer 2 and Layer 3 Switches, and Routers<\/h5>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>From AI tools as IS.<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Modern computer networks are built from several different kinds of devices and several different kinds of logical boundaries. This can become confusing because terms such as <strong>switch, router, VLAN, subnet, LAN, Layer 2, and Layer 3<\/strong> are closely related but do not mean the same thing.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A particularly common source of confusion is the relationship between a <strong>VLAN and an IP subnet<\/strong>. In a typical corporate network, one VLAN is normally paired with one IP subnet, making them look almost interchangeable. Technically, however, they operate at different layers and solve different problems.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Similarly, a modern <strong>Layer 3 switch<\/strong> can perform routing, which makes it look very much like a router. Yet Layer 3 switches and routers are normally designed for somewhat different jobs.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The easiest way to understand all of this is to start with how devices communicate on a simple Ethernet network and gradually build up from there.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">The Main Types of Network Devices<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">A modern network can include many kinds of devices.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Some of the most important are:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>end devices or hosts;<\/li>\n\n\n\n<li>servers;<\/li>\n\n\n\n<li>Ethernet switches;<\/li>\n\n\n\n<li>wireless access points;<\/li>\n\n\n\n<li>routers;<\/li>\n\n\n\n<li>firewalls;<\/li>\n\n\n\n<li>gateways;<\/li>\n\n\n\n<li>modems and optical network terminals.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">End Devices or Hosts<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">An <strong>end device<\/strong>, often called a <strong>host<\/strong>, is a device that produces or consumes network communication.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Examples include:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>desktop computers;<\/li>\n\n\n\n<li>laptops;<\/li>\n\n\n\n<li>smartphones;<\/li>\n\n\n\n<li>tablets;<\/li>\n\n\n\n<li>printers;<\/li>\n\n\n\n<li>IP phones;<\/li>\n\n\n\n<li>security cameras;<\/li>\n\n\n\n<li>smart TVs;<\/li>\n\n\n\n<li>servers;<\/li>\n\n\n\n<li>IoT devices.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">A laptop opening a website is an end device.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A smartphone making a VoIP call is an end device.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A printer receiving a print job is an end device.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Servers<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">A server is also a host, but it normally provides services to other devices.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Examples include:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>web servers;<\/li>\n\n\n\n<li>database servers;<\/li>\n\n\n\n<li>email servers;<\/li>\n\n\n\n<li>file servers;<\/li>\n\n\n\n<li>DNS servers;<\/li>\n\n\n\n<li>DHCP servers;<\/li>\n\n\n\n<li>authentication servers;<\/li>\n\n\n\n<li>application servers.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">The distinction between a client and a server is therefore mainly about the <strong>role of the device or application<\/strong>, not necessarily different hardware.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">What Does a Layer 2 Switch Do?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">An Ethernet switch primarily works at <strong>Layer 2<\/strong>, the Data Link layer.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Its basic job is to move <strong>Ethernet frames<\/strong> between devices.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A Layer 2 switch primarily makes forwarding decisions based on:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>MAC addresses<\/strong><\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">Suppose four computers are connected to one switch:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>PC-A \u2500\u2510\nPC-B \u2500\u2524\n      Switch\nPC-C \u2500\u2524\nPC-D \u2500\u2518\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">Each Ethernet network interface has a MAC address.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For example:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>PC-A = AA:AA:AA:AA:AA:AA\nPC-B = BB:BB:BB:BB:BB:BB\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">When frames arrive, the switch learns which MAC addresses are reachable through which ports.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Its MAC address table might eventually look like:<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>MAC address<\/th><th>Switch port<\/th><\/tr><\/thead><tbody><tr><td>AA:AA:AA:AA:AA:AA<\/td><td>Port 1<\/td><\/tr><tr><td>BB:BB:BB:BB:BB:BB<\/td><td>Port 2<\/td><\/tr><tr><td>CC:CC:CC:CC:CC:CC<\/td><td>Port 3<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">If a frame destined for PC-B arrives on Port 1, the switch sees:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>Destination MAC = BB:BB:BB:BB:BB:BB\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">checks its MAC address table and forwards the frame through Port 2.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This process does not require the switch to examine the destination IP address.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Ubiquiti&#8217;s current networking documentation describes the same basic process: Layer 2 switches learn source MAC addresses, build forwarding tables, and use those tables to decide where Ethernet frames should be sent.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Does a Layer 2 Switch Need an IP Address?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Interestingly:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>A basic Layer 2 switch does not need an IP address to switch Ethernet frames.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">It can learn MAC addresses and forward frames without having an IP address of its own.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For example:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>PC-A \u2500 Switch \u2500 PC-B\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">PC-A and PC-B can exchange Ethernet traffic through the switch even if the switch itself has no management IP address.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Managed switches are usually assigned an IP address so administrators can:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>connect using SSH;<\/li>\n\n\n\n<li>access a web interface;<\/li>\n\n\n\n<li>use SNMP;<\/li>\n\n\n\n<li>collect telemetry;<\/li>\n\n\n\n<li>perform configuration and monitoring.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">That IP address is for <strong>management<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">It is not what allows ordinary Layer 2 frame forwarding to happen.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Is a MAC Address Required?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">For normal Ethernet communication, <strong>MAC addresses are fundamental<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">An Ethernet frame contains source and destination MAC addresses.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For example:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>Destination MAC\nSource MAC\nEtherType\nPayload\nFrame Check Sequence\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">So Ethernet devices generally require MAC addressing to deliver frames.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">However:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>IP networking itself does not universally require MAC addresses.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">MAC addresses belong to technologies such as Ethernet.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">IP can also operate over other Layer 2 technologies that do not use Ethernet MAC addressing in the same way.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Examples include certain:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>point-to-point links;<\/li>\n\n\n\n<li>tunnels;<\/li>\n\n\n\n<li>PPP links;<\/li>\n\n\n\n<li>virtual interfaces.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Therefore:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Ethernet \u2192 normally requires MAC addressing<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">but:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>IP \u2192 does not inherently require Ethernet MAC addresses<\/strong><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Can MAC Communication Exist Without IP?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Yes.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Ethernet is not dependent on IP.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Two devices can exchange Layer 2 Ethernet frames using MAC addresses without running IPv4 or IPv6.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Various Layer 2 control protocols also operate without depending on ordinary IP forwarding.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Examples include protocols associated with:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>spanning tree;<\/li>\n\n\n\n<li>link discovery;<\/li>\n\n\n\n<li>link aggregation.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">So:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>MAC addressing can exist without IP addressing.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Can IP Exist Without Ethernet?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Yes.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">IP is a Layer 3 protocol and is not limited to Ethernet.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">An IP packet can be transported over:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Ethernet;<\/li>\n\n\n\n<li>Wi-Fi;<\/li>\n\n\n\n<li>cellular systems;<\/li>\n\n\n\n<li>point-to-point links;<\/li>\n\n\n\n<li>tunnels;<\/li>\n\n\n\n<li>many other underlying technologies.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">This is one of the great strengths of IP.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The Layer 3 packet does not need to know whether one particular segment of its journey uses copper Ethernet, fiber, Wi-Fi, or another technology.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">What Is a VLAN?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>VLAN<\/strong> means:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>Virtual Local Area Network<\/strong><\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">A VLAN logically separates one physical switched Ethernet infrastructure into multiple Layer 2 networks.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Suppose a company owns one switch:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>Port 1 \u2192 Employee PC\nPort 2 \u2192 Employee PC\nPort 3 \u2192 Accounting PC\nPort 4 \u2192 Accounting PC\nPort 5 \u2192 Guest device\nPort 6 \u2192 Guest device\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">Instead of putting everyone into the same Layer 2 network, the administrator could configure:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>VLAN 10 \u2192 Employees\nVLAN 20 \u2192 Accounting\nVLAN 30 \u2192 Guests\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">The physical switch is one device, but logically there are three separate Ethernet networks.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">A VLAN Is a Broadcast Domain<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">One important property of a VLAN is that each VLAN normally forms a separate <strong>Layer 2 broadcast domain<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Suppose a computer in VLAN 10 sends an Ethernet broadcast.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The switch forwards that broadcast to other appropriate ports in:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>VLAN 10\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">but not normally to:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>VLAN 20\nVLAN 30\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">Therefore:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>A VLAN creates Layer 2 separation.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">Devices connected to the same physical switch can behave as though they were connected to separate switches.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">One Physical Switch, Several Logical LANs<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Conceptually:<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\"> <code>              Physical Switch\n        \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510\n        \u2502 VLAN 10     VLAN 20      \u2502\n        \u2502 Staff       Accounting   \u2502\n        \u2502                          \u2502\n        \u2502 VLAN 30                  \u2502\n        \u2502 Guests                   \u2502\n        \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">This is why VLANs are so useful.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Organizations do not need a completely separate physical switch for every department or network.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">What Is an IP Subnet?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">A <strong>subnet<\/strong> is a Layer 3 concept.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">It defines a group of IP addresses belonging to the same logical IP network.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For example:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>192.168.10.0\/24\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">is an IPv4 subnet.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Addresses might include:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>192.168.10.1\n192.168.10.2\n192.168.10.3\n...\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">Another subnet could be:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>192.168.20.0\/24\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">These are different IP networks.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A router or Layer 3 device is normally required to forward packets between them.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">VLAN and Subnet: Are They the Same Thing?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">No.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">They frequently correspond to each other, but they are different concepts.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>VLAN<\/th><th>Subnet<\/th><\/tr><\/thead><tbody><tr><td>Layer 2<\/td><td>Layer 3<\/td><\/tr><tr><td>Ethernet concept<\/td><td>IP concept<\/td><\/tr><tr><td>Creates a broadcast domain<\/td><td>Defines an IP network<\/td><\/tr><tr><td>Identified by VLAN ID<\/td><td>Identified by network prefix<\/td><\/tr><tr><td>Example: VLAN 10<\/td><td>Example: <code>192.168.10.0\/24<\/code><\/td><\/tr><tr><td>Switches enforce separation<\/td><td>Routers route between subnets<\/td><\/tr><tr><td>Uses MAC-based forwarding<\/td><td>Uses IP-based forwarding<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">A good way to remember the distinction is:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>A VLAN groups and separates Ethernet devices.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">while:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>A subnet groups and separates IP addresses.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Why Do VLANs and Subnets Seem Like the Same Thing?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Because normal network design commonly maps them one-to-one.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For example:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>VLAN 10 \u2192 192.168.10.0\/24\nVLAN 20 \u2192 192.168.20.0\/24\nVLAN 30 \u2192 192.168.30.0\/24\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">This is a very clean design.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Each VLAN represents:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>one Layer 2 broadcast domain;<\/li>\n\n\n\n<li>normally one IP subnet.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Cisco documentation describes this common design explicitly: individual IP subnetworks are commonly mapped to individual VLANs, while routing is required to communicate between VLANs.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">So in practice:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>One VLAN = one subnet<\/strong><\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">is a very useful design rule.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">But it is not a definition saying VLAN and subnet are technically identical.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Does Subnetting Create VLANs?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">No.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Subnetting creates <strong>IP networks<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">It does not automatically create Layer 2 VLANs.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Consider a router:<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\"> <code>                Router\n                \/      \\\n192.168.10.0\/24          192.168.20.0\/24\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">Each router interface could connect to a separate physical Ethernet network.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">There might be no VLAN configuration anywhere.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Yet there are clearly two IP subnets.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Therefore:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>A subnet can exist without a VLAN.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Can a VLAN Exist Without a Subnet?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Yes.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A VLAN can exist entirely at Layer 2 without any IP subnet being assigned to it.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For example:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>VLAN 100\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">may be configured on a switch and contain Ethernet devices that use some non-IP protocol.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Or an administrator may create a VLAN before any devices or IP addresses have been assigned.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Therefore:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>A VLAN does not technically require an IP subnet.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">However, if hosts in that VLAN are going to use normal IPv4 or IPv6 communication, the VLAN will ordinarily be associated with an IP subnet.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Can a Network Exist Without IP?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Yes.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A computer network does not have to use Internet Protocol.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Ethernet itself is a networking technology and can carry protocols other than IPv4 or IPv6.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Historically, many networks used protocols such as:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>IPX;<\/li>\n\n\n\n<li>AppleTalk;<\/li>\n\n\n\n<li>various proprietary networking protocols.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Specialized industrial environments can also use communication mechanisms that are not ordinary IP networks.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Today, however, IP dominates general-purpose computer networking.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Can Multiple VLANs Use One IP Subnet?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Under normal network design:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>They should not.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">Suppose:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>VLAN 10\nPC-A = 192.168.1.10\/24\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">and:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>VLAN 20\nPC-B = 192.168.1.20\/24\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">Both hosts believe they are on:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>192.168.1.0\/24\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">PC-A examines:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>192.168.1.20\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">and concludes:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\">\u201cThat address belongs to my local subnet.\u201d<\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">So PC-A tries to discover PC-B&#8217;s MAC address using ARP.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">It broadcasts:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>Who has 192.168.1.20?\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">But the broadcast remains within VLAN 10.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">PC-B is in VLAN 20 and never receives it.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Communication therefore fails under normal circumstances.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This is why the normal design is:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>VLAN 10 \u2192 Subnet A\nVLAN 20 \u2192 Subnet B\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">rather than putting the same subnet into two isolated VLANs.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Specialized techniques can change this behavior, but they are exceptions rather than the normal design.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Can One VLAN Contain Multiple IP Subnets?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Technically, yes.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For example, devices in one VLAN could be configured using:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>192.168.10.0\/24\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">and:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>192.168.20.0\/24\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">on the same Layer 2 broadcast domain.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">But this is generally not the preferred design.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">It complicates:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>addressing;<\/li>\n\n\n\n<li>gateway configuration;<\/li>\n\n\n\n<li>troubleshooting;<\/li>\n\n\n\n<li>security;<\/li>\n\n\n\n<li>broadcast-domain design.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">The normal design remains:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>One VLAN mapped to one IP subnet.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">What Happens When Two Computers Are in the Same VLAN and Subnet?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Suppose:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>PC-A\nIP: 192.168.10.10\nMAC: AA-AA-AA-AA-AA-AA\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">and:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>PC-B\nIP: 192.168.10.20\nMAC: BB-BB-BB-BB-BB-BB\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">Both belong to:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>VLAN 10\nSubnet: 192.168.10.0\/24\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">and are connected through a Layer 2 switch.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The communication process is roughly as follows.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Step 1: PC-A examines the destination IP<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">PC-A sees:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>192.168.10.20\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">Its subnet mask tells it that the destination is on the same subnet.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Therefore, PC-A does <strong>not<\/strong> send the packet to its router.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Step 2: PC-A Needs the Destination MAC Address<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Ethernet delivers frames using MAC addresses.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">PC-A therefore needs to determine which MAC address corresponds to:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>192.168.10.20\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">It uses ARP for IPv4.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Conceptually:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>Who has 192.168.10.20?\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">This is transmitted as an Ethernet broadcast.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Step 3: The Switch Floods the Broadcast<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Because it is a broadcast, the switch sends it to the other ports belonging to VLAN 10.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">PC-B receives the request.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Step 4: PC-B Replies<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">PC-B responds:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>192.168.10.20 is at BB-BB-BB-BB-BB-BB\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">PC-A now knows PC-B&#8217;s MAC address.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Step 5: PC-A Builds an Ethernet Frame<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">The frame contains approximately:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>Destination MAC: BB-BB-BB-BB-BB-BB\nSource MAC:      AA-AA-AA-AA-AA-AA\n\nInside the frame:\nSource IP:       192.168.10.10\nDestination IP:  192.168.10.20\n<\/code><\/pre>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Step 6: The Layer 2 Switch Forwards the Frame<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">The switch looks at:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>Destination MAC\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">checks its MAC address table, and sends the frame toward PC-B.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The router is not involved.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This is <strong>Layer 2 switching<\/strong>.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">What If Two Physical LAN Segments Are Connected by a Layer 2 Switch?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Suppose:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>LAN Segment A \u2500\u2500\u2500 Layer 2 Switch \u2500\u2500\u2500 LAN Segment B\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">If both sides belong to the <strong>same VLAN<\/strong>, the switch can bridge Ethernet frames between them.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Conceptually, the switch has turned those physical segments into one larger Layer 2 network.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For example:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>Segment A:\nPC-A\nPC-B\n\n        Layer 2 Switch\n\nSegment B:\nPC-C\nPC-D\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">If all are in VLAN 10, they can belong to the same Layer 2 broadcast domain.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Calling them \u201cLAN A\u201d and \u201cLAN B\u201d is therefore somewhat ambiguous.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Physically, they may be separate Ethernet segments.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Logically, after bridging them through the switch, they can be one LAN.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">What If They Are Truly Separate LANs?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">If \u201cLAN 1\u201d and \u201cLAN 2\u201d means:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>LAN 1 = VLAN 10 \/ 192.168.10.0\/24\n\nLAN 2 = VLAN 20 \/ 192.168.20.0\/24\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">then a Layer 2 switch cannot by itself provide communication between them.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A <strong>Layer 3 device<\/strong> is required.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">That could be:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>a router;<\/li>\n\n\n\n<li>a Layer 3 switch;<\/li>\n\n\n\n<li>a firewall capable of routing.<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">What Is a Layer 3 Switch?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">A <strong>Layer 3 switch<\/strong> combines traditional Ethernet switching with IP routing capabilities.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">It can perform:<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Layer 2 switching<\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>MAC address \u2192 switch port\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">and:<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Layer 3 routing<\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>Destination IP network \u2192 next hop\/interface\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">Modern Layer 3 switches commonly perform routing directly in switching hardware, making inter-VLAN communication extremely fast.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Ubiquiti, for example, describes current Layer 3 switches as providing hardware-accelerated inter-VLAN routing.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">What Is an SVI?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">One common way for a Layer 3 switch to route between VLANs is through <strong>Switched Virtual Interfaces<\/strong>, usually abbreviated <strong>SVIs<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Suppose:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>VLAN 10 \u2192 192.168.10.0\/24\nVLAN 20 \u2192 192.168.20.0\/24\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">The Layer 3 switch could have:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>interface VLAN 10\nIP address 192.168.10.1\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">and:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>interface VLAN 20\nIP address 192.168.20.1\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">The hosts use those addresses as their default gateways.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Conceptually:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>VLAN 10\n192.168.10.0\/24\n       \u2502\n       \u2502 192.168.10.1\n       \u2502\n   Layer 3 Switch\n       \u2502\n       \u2502 192.168.20.1\n       \u2502\nVLAN 20\n192.168.20.0\/24\n<\/code><\/pre>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">How Does a Layer 3 Switch Move Data Between VLANs?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Suppose:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>PC-A\n192.168.10.10\/24\nVLAN 10\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">needs to contact:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>PC-B\n192.168.20.20\/24\nVLAN 20\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">PC-A examines the destination.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">It sees that:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>192.168.20.20\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">is outside its local subnet.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Therefore, rather than trying to find PC-B&#8217;s MAC address, PC-A sends the packet to its <strong>default gateway<\/strong>:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>192.168.10.1\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">which belongs to the Layer 3 switch.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">The First Ethernet Frame<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">PC-A transmits approximately:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>Ethernet:\nDestination MAC = MAC of VLAN 10 gateway\nSource MAC      = MAC of PC-A\n\nIP:\nSource IP       = 192.168.10.10\nDestination IP  = 192.168.20.20\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">Notice something very important:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\">The destination MAC address is the gateway&#8217;s MAC address, but the destination IP address remains PC-B&#8217;s IP address.<\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">The Layer 3 Switch Routes the Packet<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">The Layer 3 switch:<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li>receives the Ethernet frame;<\/li>\n\n\n\n<li>removes the Layer 2 Ethernet header;<\/li>\n\n\n\n<li>examines the destination IP address;<\/li>\n\n\n\n<li>checks its routing table;<\/li>\n\n\n\n<li>determines that <code>192.168.20.0\/24<\/code> is reachable through VLAN 20;<\/li>\n\n\n\n<li>discovers PC-B&#8217;s MAC address if necessary;<\/li>\n\n\n\n<li>constructs a new Ethernet frame;<\/li>\n\n\n\n<li>sends the packet into VLAN 20.<\/li>\n<\/ol>\n\n\n\n<p class=\"wp-block-paragraph\">The new frame might contain:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>Destination MAC = PC-B's MAC\nSource MAC      = Layer 3 switch VLAN 20 MAC\n\nSource IP       = 192.168.10.10\nDestination IP  = 192.168.20.20\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">The Ethernet addresses changed.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The source and destination IP addresses normally did not.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This illustrates a fundamental principle:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>MAC addresses normally change as packets cross routed Layer 3 boundaries, while end-to-end IP addresses normally remain the same unless something such as NAT changes them.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Layer 2 Switch vs. Layer 3 Switch<\/h1>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Capability<\/th><th>Layer 2 Switch<\/th><th>Layer 3 Switch<\/th><\/tr><\/thead><tbody><tr><td>Ethernet switching<\/td><td>Yes<\/td><td>Yes<\/td><\/tr><tr><td>MAC address table<\/td><td>Yes<\/td><td>Yes<\/td><\/tr><tr><td>VLANs<\/td><td>Yes<\/td><td>Yes<\/td><\/tr><tr><td>Layer 2 broadcast separation<\/td><td>Yes<\/td><td>Yes<\/td><\/tr><tr><td>IP routing<\/td><td>Normally no<\/td><td>Yes<\/td><\/tr><tr><td>Routing table<\/td><td>Normally no forwarding role<\/td><td>Yes<\/td><\/tr><tr><td>Inter-VLAN routing<\/td><td>No<\/td><td>Yes<\/td><\/tr><tr><td>SVI\/default gateway<\/td><td>Management only or limited<\/td><td>Yes<\/td><\/tr><tr><td>Static\/dynamic routes<\/td><td>No or very limited<\/td><td>Usually supported to varying degrees<\/td><\/tr><tr><td>Typical use<\/td><td>Access switching<\/td><td>Distribution\/core + access in some designs<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">Cisco&#8217;s training material similarly contrasts a Layer 2 Catalyst 2960 with a Layer 3-capable switch and notes that enabling IP routing allows the Layer 3 switch to perform routing functions.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">What Is a Router?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">A <strong>router<\/strong> is fundamentally a Layer 3 device.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Its main job is:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>to connect different IP networks and forward packets between them based on destination IP addresses and routing information.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">For example:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>LAN A\n192.168.10.0\/24\n      \u2502\n    Router\n      \u2502\nLAN B\n192.168.20.0\/24\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">or:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>Corporate LAN\n      \u2502\n    Router\n      \u2502\n     ISP\n      \u2502\n   Internet\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">Routers maintain routing tables showing how different networks can be reached.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">A Router Is Not Defined as \u201cLAN to WAN\u201d<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">It is common to think:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>Switch = LAN\nRouter = LAN to Internet\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">That is an oversimplification.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A router can connect:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>LAN to LAN;<\/li>\n\n\n\n<li>subnet to subnet;<\/li>\n\n\n\n<li>VLAN to VLAN;<\/li>\n\n\n\n<li>LAN to WAN;<\/li>\n\n\n\n<li>WAN to WAN;<\/li>\n\n\n\n<li>branch office to headquarters;<\/li>\n\n\n\n<li>enterprise network to ISP;<\/li>\n\n\n\n<li>one ISP to another ISP.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">For example, two subnets inside the same building may communicate through a router.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">No WAN is necessary.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">If a Layer 3 Switch Routes, Why Do We Need Routers?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">This is an important question.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A modern Layer 3 switch and a router overlap substantially.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Both can:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>maintain routing tables;<\/li>\n\n\n\n<li>forward IP packets;<\/li>\n\n\n\n<li>support static routes;<\/li>\n\n\n\n<li>support routing protocols;<\/li>\n\n\n\n<li>route between networks.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">The difference is increasingly about <strong>design, interfaces, features, scale, and intended role<\/strong> rather than a rigid Layer 2-versus-Layer 3 distinction.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Layer 3 Switch: Optimized for High-Speed LAN Routing<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Layer 3 switches are commonly optimized for:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>many Ethernet ports;<\/li>\n\n\n\n<li>very high switching throughput;<\/li>\n\n\n\n<li>VLANs;<\/li>\n\n\n\n<li>inter-VLAN routing;<\/li>\n\n\n\n<li>campus networks;<\/li>\n\n\n\n<li>data centres;<\/li>\n\n\n\n<li>access\/distribution\/core switching.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">For example:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>Employees VLAN\n          \\\nServers VLAN \u2500 Layer 3 Switch \u2500 Campus Core\n          \/\nGuest VLAN\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">The device can switch and route enormous volumes of traffic locally.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Router: Optimized for Connecting Networks and WANs<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Routers are typically designed for broader Layer 3 connectivity.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Depending on the router, features may include:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>sophisticated routing protocols;<\/li>\n\n\n\n<li>BGP;<\/li>\n\n\n\n<li>MPLS;<\/li>\n\n\n\n<li>WAN interfaces;<\/li>\n\n\n\n<li>VPN;<\/li>\n\n\n\n<li>SD-WAN;<\/li>\n\n\n\n<li>NAT;<\/li>\n\n\n\n<li>QoS;<\/li>\n\n\n\n<li>tunneling;<\/li>\n\n\n\n<li>traffic engineering;<\/li>\n\n\n\n<li>carrier-scale routing tables;<\/li>\n\n\n\n<li>Internet peering;<\/li>\n\n\n\n<li>cellular WAN connections.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">A branch router, for example, may connect:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>Office LAN\n    \u2502\nBranch Router\n    \u251c\u2500\u2500 Fiber ISP\n    \u251c\u2500\u2500 Secondary ISP\n    \u2514\u2500\u2500 5G Backup\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">That role is different from simply switching thousands of local Ethernet devices.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Layer 3 Switch vs. Router<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">A useful practical comparison is:<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Layer 3 Switch<\/th><th>Router<\/th><\/tr><\/thead><tbody><tr><td>Primarily optimized for LAN\/campus\/data-centre Ethernet<\/td><td>Primarily optimized for inter-network\/WAN\/edge routing<\/td><\/tr><tr><td>Usually many Ethernet switch ports<\/td><td>Often fewer but more flexible routed interfaces<\/td><\/tr><tr><td>Extremely fast inter-VLAN routing<\/td><td>Rich WAN and routing capabilities<\/td><\/tr><tr><td>Common in campus distribution\/core<\/td><td>Common at network boundaries and WAN edges<\/td><\/tr><tr><td>Heavy emphasis on VLANs<\/td><td>Heavy emphasis on routing<\/td><\/tr><tr><td>Often ASIC-based local forwarding<\/td><td>Also hardware accelerated on modern enterprise\/provider routers<\/td><\/tr><tr><td>Usually does not perform Internet NAT\/firewall duties as its primary role<\/td><td>May provide NAT, VPN, WAN, SD-WAN and related services<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">But these are tendencies\u2014not absolute laws.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Modern high-end networking hardware increasingly blurs the distinction.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Can a Layer 3 Switch Replace a Router?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Sometimes.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Consider an office containing several VLANs:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>Staff VLAN\nFinance VLAN\nServer VLAN\nGuest VLAN\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">A Layer 3 switch can route among these networks efficiently.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">There may be no reason to send every internal packet through a separate external router.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For example:<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\"> <code>             Layer 3 Switch\n              \/     |      \\\n          Staff   Servers   Finance\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">This is one of the most common uses of Layer 3 switching.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">But when traffic needs to leave the organization:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>Layer 3 Switch\n      \u2502\nFirewall \/ Edge Router\n      \u2502\nISP\n      \u2502\nInternet\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">a dedicated edge router, firewall, or integrated security gateway is often used.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Can a Router Perform Layer 2 Switching?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Some routers can.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Modern network appliances frequently combine many functions.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">One physical box might contain:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>router;<\/li>\n\n\n\n<li>Ethernet switch;<\/li>\n\n\n\n<li>firewall;<\/li>\n\n\n\n<li>VPN gateway;<\/li>\n\n\n\n<li>Wi-Fi access point;<\/li>\n\n\n\n<li>DHCP server.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">A typical home \u201cwireless router\u201d is a good example.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Internally, it often contains:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>Router\n+\nEthernet switch\n+\nWi-Fi access point\n+\nFirewall\/NAT\n+\nDHCP server\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">So the product name does not necessarily reveal every internal function.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">What Is an Access Switch?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">An <strong>access switch<\/strong> connects end devices to the network.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Examples include:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>desktop computers;<\/li>\n\n\n\n<li>printers;<\/li>\n\n\n\n<li>IP phones;<\/li>\n\n\n\n<li>Wi-Fi access points;<\/li>\n\n\n\n<li>security cameras.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">A typical corporate access layer looks like:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>PC \u2500\u2510\nIP Phone \u2500\u2524\nPrinter \u2500\u2500\u2524 Access Switch\nWi-Fi AP \u2500\u2524\nCamera \u2500\u2500\u2500\u2518\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">Access switches often provide <strong>Power over Ethernet (PoE)<\/strong> so the Ethernet cable can provide both data and electrical power to:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>IP phones;<\/li>\n\n\n\n<li>access points;<\/li>\n\n\n\n<li>cameras.<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Distribution and Core Switches<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Larger networks often use hierarchical designs.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A simplified traditional campus architecture is:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>End Devices\n     \u2502\nAccess Switches\n     \u2502\nDistribution Switches\n     \u2502\nCore\n     \u2502\nWAN\/Internet\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">Distribution and core switches are often Layer 3 switches.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">They can route between many VLANs and aggregate traffic from many access switches.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Current Cisco campus families illustrate this separation. Cisco positions Catalyst 9200 and 9300 systems for access and branch\/campus use, while Catalyst 9400, 9500, and 9600 families serve increasingly large distribution and core roles.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">A Small-Business Network<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">A small office might have only:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>Internet\n   \u2502\nRouter\/Firewall\n   \u2502\nManaged Switch\n \u250c\u2500\u253c\u2500\u2500\u2500\u2500\u252c\u2500\u2500\u2500\u2500\u2500\u2510\nPC AP Printer Phone\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">The router\/firewall might perform:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Internet routing;<\/li>\n\n\n\n<li>NAT;<\/li>\n\n\n\n<li>DHCP;<\/li>\n\n\n\n<li>VPN;<\/li>\n\n\n\n<li>firewalling.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">The switch provides:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Ethernet connectivity;<\/li>\n\n\n\n<li>VLANs;<\/li>\n\n\n\n<li>PoE;<\/li>\n\n\n\n<li>perhaps some Layer 3 functionality.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Current examples aimed at smaller environments include Cisco Catalyst 1300 switches, which Cisco describes as designed for small and medium-sized businesses.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Cloud-managed platforms are also common in this market. Cisco Meraki, for example, offers smaller security\/SD-WAN appliances for branches ranging from tens to hundreds of users.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Ubiquiti UniFi is another commonly encountered architecture in small and medium environments, offering Layer 2 and Layer 3 switching along with gateway and Wi-Fi systems.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">A Medium-Sized Corporate Network<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">A medium-sized organization might have:<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\"> <code>                  Internet\n                      \u2502\n              Firewall\/Edge Router\n                      \u2502\n               Layer 3 Core\n                \/           \\\n       Access Switch     Access Switch\n       \/   |    \\          \/   |    \\\n     PCs  APs  Phones    PCs  APs  Cameras\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">There may be several VLANs:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>VLAN 10 \u2192 Corporate users\nVLAN 20 \u2192 Voice\nVLAN 30 \u2192 Servers\nVLAN 40 \u2192 Wi-Fi\nVLAN 50 \u2192 Guests\nVLAN 60 \u2192 Cameras\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">A Layer 3 switch may route among these networks.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A firewall may control which VLANs are permitted to communicate.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The edge router or firewall handles connectivity toward:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Internet providers;<\/li>\n\n\n\n<li>branch offices;<\/li>\n\n\n\n<li>cloud services;<\/li>\n\n\n\n<li>VPNs.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Representative current enterprise switching platforms include Cisco Catalyst 9200 and 9300 systems. Cisco describes the 9200 family as enterprise access switching for branches and midsize campuses and the 9300 family as campus access systems with greater scale and capabilities.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For branch\/WAN routing, Cisco&#8217;s current Catalyst 8300 platform is designed for SD-WAN, SASE, 5G and cloud-edge applications.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">A Large Corporate Campus<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">A large corporation may have thousands or tens of thousands of devices.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A simplified architecture could be:<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\"> <code>                   Internet \/ WAN\n                         \u2502\n                   Edge Routers\n                         \u2502\n                     Firewalls\n                         \u2502\n                 Core L3 Switches\n                  \/             \\\n         Distribution       Distribution\n          \/       \\           \/       \\\n       Access    Access    Access    Access\n        \u2502          \u2502        \u2502          \u2502\n     Users\/APs  Phones    Servers    Cameras\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">At this scale, redundancy becomes essential.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Organizations may use:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>redundant core switches;<\/li>\n\n\n\n<li>redundant routers;<\/li>\n\n\n\n<li>multiple ISPs;<\/li>\n\n\n\n<li>dynamic routing protocols;<\/li>\n\n\n\n<li>high-speed fiber links;<\/li>\n\n\n\n<li>link aggregation;<\/li>\n\n\n\n<li>hundreds or thousands of VLANs;<\/li>\n\n\n\n<li>large routing tables.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Cisco currently positions Catalyst 9500 and 9600 systems for midsize-to-large campus core roles.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">What Happens in a Data Centre?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Data-centre networks can be much larger and faster.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Instead of the traditional access\/distribution\/core hierarchy, many data centres use <strong>leaf-spine architectures<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A simplified model is:<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\"> <code>      Spine     Spine\n        \/|\\       \/|\\\n       \/ | \\     \/ | \\\n    Leaf Leaf  Leaf Leaf\n     \u2502    \u2502     \u2502    \u2502\n   Servers     Servers\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">These devices often perform both sophisticated Layer 2 and Layer 3 functions.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Cisco&#8217;s Nexus 9000 family, for example, is designed for data-centre switching and currently supports interfaces reaching 800 Gb\/s on some platforms.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">At this scale, the old idea that:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\">\u201cswitch = simple Layer 2 device\u201d<\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">becomes increasingly inadequate.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Modern data-centre switches often perform extensive Layer 3 routing as well.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">What Devices Make Up the Internet?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">The Internet is fundamentally a <strong>network of networks<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A simplified path might be:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>Home\/Office\n    \u2502\nAccess Router\n    \u2502\nISP Edge Router\n    \u2502\nISP Core\n    \u2502\nInternet Peering Router\n    \u2502\nAnother ISP\n    \u2502\nData Centre\n    \u2502\nServer\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">Internet-scale routers must manage enormous quantities of traffic and very large routing tables.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">They commonly use:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>BGP;<\/li>\n\n\n\n<li>MPLS;<\/li>\n\n\n\n<li>segment routing;<\/li>\n\n\n\n<li>high-speed optical Ethernet;<\/li>\n\n\n\n<li>100G;<\/li>\n\n\n\n<li>400G;<\/li>\n\n\n\n<li>increasingly 800G links.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Representative service-provider platforms include Cisco&#8217;s 8000 Series and Juniper&#8217;s MX and PTX families.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Cisco positions its 8000 systems for carrier core, aggregation and Internet peering applications.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Juniper&#8217;s MX family is used for service-provider edge, broadband, peering and related applications, while the PTX family is designed for high-capacity core and WAN environments. Current PTX platforms support 400G and 800G architectures.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Are There Switches Inside the Internet?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Certainly.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The Internet is not built only from routers.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Switches are heavily used inside:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>data centres;<\/li>\n\n\n\n<li>ISP facilities;<\/li>\n\n\n\n<li>Internet exchanges;<\/li>\n\n\n\n<li>carrier Ethernet networks;<\/li>\n\n\n\n<li>aggregation networks.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">The distinction depends on what function is being performed at that point.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For communication between IP networks or autonomous systems, routing is central.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Within a data-centre fabric or local Layer 2 domain, switching may be central.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Modern hardware can perform both.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Common Equipment in Networking Labs<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Networking laboratories often use either real hardware or network simulators\/emulators.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Historically and still in many training environments, Cisco devices such as:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Catalyst 2960 Layer 2 switches;<\/li>\n\n\n\n<li>Catalyst 3560\/3650 Layer 3 switches;<\/li>\n\n\n\n<li>Cisco 1941\/2900-series routers<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">are frequently encountered.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">These should be understood as <strong>training and legacy platforms<\/strong>, not necessarily recommendations for new corporate deployments in 2026.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Cisco&#8217;s own networking lab material has used Catalyst 2960 switches and Cisco ISR routers in hands-on exercises, while Layer 2-versus-Layer 3 comparison material uses the 2960 alongside Layer 3-capable Catalyst platforms.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Today, many labs are also virtual.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Common approaches include:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Cisco Packet Tracer;<\/li>\n\n\n\n<li>GNS3;<\/li>\n\n\n\n<li>EVE-NG;<\/li>\n\n\n\n<li>vendor virtual router images;<\/li>\n\n\n\n<li>cloud networking labs.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Virtual labs make it possible to construct networks containing many routers and switches without owning large amounts of physical hardware.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Representative Devices by Environment<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">The following is not a strict purchasing guide; it illustrates the kinds of equipment encountered at different scales.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Environment<\/th><th>Typical switching<\/th><th>Typical routing\/gateway role<\/th><\/tr><\/thead><tbody><tr><td>Home<\/td><td>Integrated Ethernet switch<\/td><td>Consumer gateway\/router<\/td><\/tr><tr><td>Small business<\/td><td>Managed L2\/L3 switch<\/td><td>Firewall\/router appliance<\/td><\/tr><tr><td>Medium enterprise<\/td><td>Enterprise access switches<\/td><td>Branch router\/firewall<\/td><\/tr><tr><td>Large campus<\/td><td>Access + L3 distribution\/core<\/td><td>Enterprise WAN edge routers<\/td><\/tr><tr><td>Data centre<\/td><td>High-speed L2\/L3 leaf-spine switches<\/td><td>Edge\/peering routers<\/td><\/tr><tr><td>ISP<\/td><td>Carrier Ethernet\/aggregation switches<\/td><td>Edge\/core\/peering routers<\/td><\/tr><tr><td>Internet backbone<\/td><td>Very high-capacity switching fabrics<\/td><td>Carrier-class BGP\/core routers<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">Representative current families include:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Small\/medium switching:<\/strong> Cisco Catalyst 1300, Catalyst 9200, UniFi switching;<\/li>\n\n\n\n<li><strong>Enterprise campus:<\/strong> Cisco Catalyst 9300, 9400, 9500, 9600;<\/li>\n\n\n\n<li><strong>Branch\/WAN:<\/strong> Cisco Catalyst 8300 and comparable platforms;<\/li>\n\n\n\n<li><strong>Data centre:<\/strong> Cisco Nexus 9000, Juniper QFX and comparable systems;<\/li>\n\n\n\n<li><strong>Service-provider edge\/core:<\/strong> Cisco 8000, Juniper MX and PTX.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Cisco&#8217;s current Catalyst portfolio explicitly divides its families among access, distribution, and core roles, while Juniper positions its MX\/PTX families for edge, peering, WAN and core routing.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Putting VLAN, Subnet, Switch and Router Together<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Consider a corporate network with three departments.<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>Employees\nVLAN 10\n192.168.10.0\/24\n       \\\n        \\\n         Layer 3 Switch\n        \/       |       \\\nAccounting      |       Servers\nVLAN 20         |       VLAN 30\n192.168.20.0\/24 |       192.168.30.0\/24\n                |\n             Firewall\n                |\n             Router\n                |\n              ISP\n                |\n             Internet\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">This architecture demonstrates all of the concepts.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Inside VLAN 10<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Frames are switched using MAC addresses.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Between VLAN 10 and VLAN 20<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Packets are routed using IP addresses.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Between the company and the Internet<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A router\/firewall forwards traffic toward the ISP.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">VLAN<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Defines the Layer 2 logical network.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Subnet<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Defines the Layer 3 IP network.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Layer 2 switch<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Moves frames within VLANs.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Layer 3 switch<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Moves frames within VLANs <strong>and<\/strong> routes packets between IP subnets.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Router<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Connects IP networks and is commonly used at WAN and Internet boundaries.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">What Addresses Are Actually Used During Communication?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">A useful summary is:<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Inside one Ethernet LAN<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Both are used:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>IP address \u2192 identifies the Layer 3 endpoint\n\nMAC address \u2192 identifies the local Ethernet destination\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">Suppose:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>192.168.10.10\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">sends something to:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>192.168.10.20\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">The IP addresses identify the endpoints.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The MAC addresses allow the Ethernet frame to cross the local LAN.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Across a Router<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Suppose:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>192.168.10.10\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">communicates with:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>8.8.8.8\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">The destination is not local.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The computer creates a frame whose:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>Destination IP  = 8.8.8.8\nDestination MAC = MAC address of local gateway\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">The router receives it.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">At the next Ethernet link, a <strong>different pair of MAC addresses<\/strong> is normally used.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Therefore:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>IP addresses identify Layer 3 source\/destination communication, while MAC addresses generally identify the next Ethernet hop.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">That is why MAC addresses normally change at routed boundaries while IP addresses can remain end-to-end.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Does Every Router Need a MAC Address?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Not inherently.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A router performing IP routing over Ethernet has MAC addresses on its Ethernet interfaces because Ethernet requires them.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">But a router could also have a non-Ethernet point-to-point interface where Ethernet MAC addressing is irrelevant.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">So:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>Routing requires Layer 3 addressing, but Ethernet MAC addressing is only required when the relevant link technology is Ethernet or uses comparable MAC mechanisms.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Does Every Switch Need an IP Address?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">No.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A Layer 2 switch can forward frames with no IP address configured.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A managed switch normally receives an IP address so administrators can manage it.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A Layer 3 switch, however, needs Layer 3 addresses on interfaces or SVIs when it is actually performing IP routing.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">The Most Important Relationships<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">These concepts can be summarized as:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>Layer 2\n    \u2502\n    \u251c\u2500\u2500 Ethernet\n    \u251c\u2500\u2500 MAC addresses\n    \u251c\u2500\u2500 Switch\n    \u2514\u2500\u2500 VLAN\n              \u2502\n              \u2502 commonly mapped 1:1\n              \u25bc\nLayer 3\n    \u2502\n    \u251c\u2500\u2500 IPv4 \/ IPv6\n    \u251c\u2500\u2500 IP addresses\n    \u251c\u2500\u2500 Subnet\n    \u251c\u2500\u2500 Layer 3 switch\n    \u2514\u2500\u2500 Router\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">This one-to-one VLAN-to-subnet relationship is a <strong>design convention<\/strong>, not a statement that VLAN and subnet are identical.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Common Misconceptions<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Several statements sound reasonable but are technically incorrect.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u201cA VLAN is a subnet.\u201d<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Not exactly.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A VLAN is Layer 2.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A subnet is Layer 3.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">They are normally paired.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">\u201cSubnetting creates VLANs.\u201d<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">No.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Subnetting creates IP subnets.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">VLANs are configured separately at Layer 2.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">\u201cA VLAN requires IP.\u201d<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">No.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A VLAN can exist without IP.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">\u201cIP requires Ethernet MAC addresses.\u201d<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">No.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">IP can operate over technologies other than Ethernet.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">\u201cA Layer 2 switch requires an IP address.\u201d<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">No.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">It requires no IP address for ordinary frame forwarding.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">\u201cA switch connects devices while a router connects LANs.\u201d<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Too simplistic.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A Layer 3 switch can route between networks, and a router can connect networks within the same building.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">\u201cRouters are only for LAN-to-WAN communication.\u201d<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">No.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A router can connect any appropriate different Layer 3 networks.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">\u201cDifferent VLANs can normally use the same subnet.\u201d<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">No.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Separate VLANs isolate Layer 2 broadcasts such as ARP, so one IP subnet spread across independently isolated VLANs normally will not function correctly without special mechanisms.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">A Useful Mental Model<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">The simplest way to keep everything straight is to ask three different questions.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Question 1: What Layer 2 network am I in?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Think:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>VLAN<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">and:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>MAC address<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">and:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>switch<\/strong><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Question 2: What Layer 3 network am I in?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Think:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>subnet<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">and:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>IP address<\/strong><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Question 3: How do I reach another Layer 3 network?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Think:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>router<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">or:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Layer 3 switch<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">and:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>default gateway<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">and:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>routing table<\/strong><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Final Thought<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">The boundaries between switches and routers have become less rigid as networking hardware has evolved.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A traditional Layer 2 switch primarily forwards:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Ethernet frames based on MAC addresses.<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A router primarily forwards:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>IP packets between networks based on IP addresses and routing tables.<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A Layer 3 switch combines both capabilities:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Layer 2 switching + Layer 3 routing.<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Likewise, a VLAN and a subnet often appear together but represent different things:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>VLAN = Layer 2 logical separation<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Subnet = Layer 3 logical addressing<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The normal modern design is:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>One VLAN\n   \u2193\nOne IP subnet\n   \u2193\nLayer 3 gateway\n   \u2193\nOther VLANs\/subnets\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">Within the VLAN, switches use MAC addresses.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Between subnets, routers or Layer 3 switches use IP addresses.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">At the edge of the organization, routers, firewalls, or integrated gateways connect the internal network to WANs, service providers, cloud networks, and ultimately the Internet.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Once these layers are separated conceptually, much of networking becomes easier to understand:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>MAC addresses and VLANs organize local Layer 2 communication. IP addresses and subnets organize Layer 3 communication. Switches move frames locally. Routers and Layer 3 switches move packets between networks.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">Modern networking equipment may combine these functions in one physical device, but the underlying concepts remain distinct.<\/p>\n\n\n\n<h1 class=\"wp-block-heading\">References and Further Reading<\/h1>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Cisco \u2014 Catalyst 9000 Switching Family.<\/strong> Current enterprise access, distribution, and core switching families, including Catalyst 9200, 9300, 9400, 9500, and 9600.<\/li>\n\n\n\n<li><strong>Cisco \u2014 Campus LAN Core and Distribution Switches.<\/strong> Current positioning of enterprise Layer 3 switching platforms for small, midsize, and large campus networks.<\/li>\n\n\n\n<li><strong>Cisco \u2014 Catalyst 8300 Series Edge Platforms.<\/strong> Current enterprise branch, SD-WAN, WAN edge, security, and 5G-capable routing platform.<\/li>\n\n\n\n<li><strong>Cisco \u2014 Nexus 9000 Series.<\/strong> Modern high-performance data-centre switching platforms supporting high-speed Ethernet up to 800G on current systems.<\/li>\n\n\n\n<li><strong>Cisco \u2014 Cisco 8000 Series.<\/strong> Carrier-class routing platforms designed for core, aggregation, peering, ISP and cloud-scale applications.<\/li>\n\n\n\n<li><strong>Cisco Networking Academy \u2014 Comparing Layer 2 and Layer 3 Devices.<\/strong> Discussion of Layer 2 switches, Layer 3 switches and routers, including inter-VLAN routing concepts.<\/li>\n\n\n\n<li><strong>Cisco \u2014 VLAN and IP Routing Configuration.<\/strong> Documentation explaining that hosts within the same VLAN can communicate through switching while communication between different VLANs requires Layer 3 routing.<\/li>\n\n\n\n<li><strong>Juniper Networks \u2014 MX Series Universal Routing Platforms.<\/strong> Service-provider and enterprise routing systems for broadband edge, peering, mobile backhaul and data-centre edge roles.<\/li>\n\n\n\n<li><strong>Juniper Networks \u2014 PTX Series Routers.<\/strong> High-capacity WAN\/core and peering platforms supporting current 100G, 400G and 800G architectures.<\/li>\n\n\n\n<li><strong>Ubiquiti \u2014 Switching, Routing and STP.<\/strong> Modern explanation of Layer 2 MAC learning and Layer 3 routing concepts.<\/li>\n\n\n\n<li><strong>Ubiquiti \u2014 Layer 3 Routing.<\/strong> Documentation showing practical inter-VLAN routing using Layer 3 switches.<\/li>\n\n\n\n<li><strong>Cisco \u2014 Catalyst 1300 Series.<\/strong> Managed switching family aimed at small and medium-sized business networks.<\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"<p>Network Devices, VLANs, Subnets, Layer 2 and Layer 3 Switches, and Routers From AI tools as IS. Modern computer networks are built from several different kinds of devices and several different kinds of logical boundaries. This can become confusing because terms such as switch, router, VLAN, subnet, LAN, Layer 2, and Layer 3 are closely &hellip; <\/p>\n<p><a class=\"more-link btn\" href=\"http:\/\/bangla.sitestree.com\/?p=78826\">Continue reading<\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_post_was_ever_published":false},"categories":[1978,265],"tags":[],"class_list":["post-78826","post","type-post","status-publish","format-standard","hentry","category-computer-networks","category-telecommunications","item-wrap"],"jetpack_sharing_enabled":true,"jetpack-related-posts":[{"id":71266,"url":"http:\/\/bangla.sitestree.com\/?p=71266","url_meta":{"origin":78826,"position":0},"title":"Difference: Auto-Regressive and Auto Correlation.","author":"Sayed","date":"September 27, 2021","format":false,"excerpt":"If you can, answer the question below: Write your answer in the comment box. 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