{"id":119457,"date":"2025-01-07T14:06:10","date_gmt":"2025-01-07T19:06:10","guid":{"rendered":"https:\/\/jumpcloud.com\/?post_type=it-index&#038;p=119457"},"modified":"2025-01-15T12:35:41","modified_gmt":"2025-01-15T17:35:41","slug":"what-is-vlan-trunking","status":"publish","type":"it-index","link":"https:\/\/jumpcloud.com\/it-index\/what-is-vlan-trunking","title":{"rendered":"What Is VLAN Trunking?"},"content":{"rendered":"\n<p>Managing a network isn&#8217;t just about hardware and bandwidth. Businesses need to control traffic, make the best use of bandwidth, and improve security. VLAN trunking is a networking tool that can help. In this post, we\u2019ll cover what VLAN trunking is, how to set it up, and important security tips to keep in mind.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Why VLAN Trunking Matters&nbsp;<\/strong><\/h3>\n\n\n\n<p>VLAN trunking is a networking feature that allows multiple Virtual Local Area Networks (VLANs) to traverse a single physical connection. By tagging network traffic with VLAN information, devices such as switches and routers can manage and isolate traffic without needing a dedicated port for each VLAN.<\/p>\n\n\n\n<ul>\n<li><strong>Enhanced Network Scalability<\/strong>: VLAN trunking reduces the need for excessive physical connections by consolidating multiple VLANs into a single trunk link.&nbsp;<\/li>\n\n\n\n<li><strong>Optimized Traffic Management<\/strong>: It enables better segmentation and prioritization of network traffic.&nbsp;<\/li>\n\n\n\n<li><strong>Simplified Infrastructure<\/strong>: VLAN trunking minimizes hardware requirements, reducing costs and complexity.<\/li>\n<\/ul>\n\n\n\n<p>This technology is widely used in enterprise environments to address the demands of growing network infrastructures and is a critical tool in network segmentation and bandwidth optimization.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Technical Definition and Purpose&nbsp;<\/strong><\/h2>\n\n\n\n<p>VLAN trunking allows data to move between different VLANs using a shared trunk link, while keeping each VLAN&#8217;s traffic separate and organized across the network.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Trunk Ports and Their Role&nbsp;<\/strong><\/h3>\n\n\n\n<p>A trunk port is a switch port configured to handle data from multiple VLANs. Unlike access ports, which connect to devices in a single VLAN, trunk ports use <strong><a href=\"https:\/\/jumpcloud.com\/blog\/untagged-vs-tagged-vlan\">VLAN tagging<\/a><\/strong> to identify and direct traffic to the correct VLAN as it traverses the network.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>VLAN Trunking in Context&nbsp;<\/strong><\/h3>\n\n\n\n<p>VLAN trunking fits into a broader strategy of network segmentation. It enhances traffic isolation, improves security, and ensures efficient communication between departments or organizational units.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>How VLAN Trunking Works&nbsp;<\/strong><\/h2>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Step 1: VLAN Tagging&nbsp;<\/strong><\/h3>\n\n\n\n<p><strong>VLAN tagging<\/strong> is the process of adding identification metadata to Ethernet frames. The industry-standard protocol for this is <a href=\"https:\/\/jumpcloud.com\/it-index\/what-is-802-1q\">IEEE 802.1Q<\/a>, which inserts a VLAN tag into the frame header.<\/p>\n\n\n\n<h4 class=\"wp-block-heading\"><strong>Key Components of a Tagged Frame&nbsp;<\/strong><\/h4>\n\n\n\n<ul>\n<li><strong><a href=\"https:\/\/jumpcloud.com\/it-index\/what-is-a-tag-protocol-identifier-tpid\">Tag Protocol Identifier (TPID)<\/a><\/strong>: Indicates the frame is tagged.\u00a0<\/li>\n\n\n\n<li><strong><a href=\"https:\/\/jumpcloud.com\/it-index\/what-is-a-priority-code-point-pcp\">Priority Code Point (PCP)<\/a><\/strong>: Used for Quality of Service (QoS) prioritization.\u00a0<\/li>\n\n\n\n<li><strong><a href=\"https:\/\/jumpcloud.com\/it-index\/what-is-vlan-id\">VLAN ID (VID)<\/a><\/strong>: Specifies the VLAN to which the frame belongs.<\/li>\n<\/ul>\n\n\n\n<p>For example, when a device sends a frame through a <a href=\"https:\/\/jumpcloud.com\/it-index\/what-is-a-trunk-port\">trunk port<\/a>, the switch appends a VLAN tag, enabling other switches and routers to direct the frame to the correct VLAN on the receiving end.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Step 2: Handling Untagged Traffic&nbsp;<\/strong><\/h3>\n\n\n\n<p>Trunk ports can also handle untagged traffic through a concept called the <strong><a href=\"https:\/\/jumpcloud.com\/it-index\/what-is-native-vlan\">native VLAN<\/a><\/strong>. Frames sent through the trunk port without tags are assigned to the native VLAN, ensuring backward compatibility with devices that don\u2019t support tagging.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Step 3: Trunk Links vs. Access Links&nbsp;<\/strong><\/h3>\n\n\n\n<p>Trunk links differ significantly from access links:<\/p>\n\n\n\n<ul>\n<li><strong>Trunk Links<\/strong>: Carry data for multiple VLANs using tagging.&nbsp;<\/li>\n\n\n\n<li><strong>Access Links<\/strong>: Limited to a single VLAN, connecting end devices like computers or printers.&nbsp;<\/li>\n<\/ul>\n\n\n\n<p>For network administrators, understanding this distinction is crucial when configuring ports for specific roles.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Configuration Basics&nbsp;<\/strong><\/h2>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Setting Up VLAN Trunking&nbsp;<\/strong><\/h3>\n\n\n\n<p>Configuring VLAN trunking requires specifying trunk modes and VLAN assignments in the Command Line Interface (CLI) of networking devices. Below is an example configuration on a Cisco switch:<\/p>\n\n\n\n<p><code>Switch(config)# interface GigabitEthernet0\/1<br>Switch(config-if)# switchport mode trunk<br>Switch(config-if)# switchport trunk allowed vlan 10,20,30<br>Switch(config-if)# switchport trunk native vlan 1<br>Switch(config-if)# end<\/code><\/p>\n\n\n\n<h4 class=\"wp-block-heading\"><strong>Key Commands Explained&nbsp;<\/strong><\/h4>\n\n\n\n<ul>\n<li><code>switchport mode trunk<\/code>: Enables trunking on the port.&nbsp;<\/li>\n\n\n\n<li><code>switchport trunk allowed vlan<\/code>: Specifies which VLANs can traverse the link.&nbsp;<\/li>\n\n\n\n<li><code>switchport trunk native vlan<\/code>: Sets the native VLAN for untagged traffic.<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Tips for Successful Configuration&nbsp;<\/strong><\/h3>\n\n\n\n<ul>\n<li><strong>Enable Trunking on Both Ends<\/strong>: Both switches on a trunk link must be configured for trunking to ensure proper communication.&nbsp;<\/li>\n\n\n\n<li><strong>Match Native VLANs<\/strong>: Native VLAN mismatches can result in dropped packets and network issues.<\/li>\n<\/ul>\n\n\n\n<p>Configuration mistakes can interrupt communication between VLANs, so testing the setup is always a best practice.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Security Considerations&nbsp;<\/strong><\/h2>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Risks of VLAN Trunking&nbsp;<\/strong><\/h3>\n\n\n\n<p>VLAN trunking improves efficiency, but it can also create risks like <strong><a href=\"https:\/\/jumpcloud.com\/it-index\/what-is-vlan-hopping\">VLAN hopping attacks<\/a><\/strong>, where attackers exploit weaknesses in VLAN tagging to access unauthorized traffic.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Mitigation Strategies&nbsp;<\/strong><\/h3>\n\n\n\n<ul>\n<li><strong>Disable Unused Trunk Ports<\/strong>: To prevent unauthorized access.&nbsp;<\/li>\n\n\n\n<li><strong>Configure Allowed VLANs<\/strong>: Specify VLANs allowed on trunk links to limit traffic.&nbsp;<\/li>\n\n\n\n<li><strong>VLAN Pruning<\/strong>: Remove unnecessary VLANs from trunk links to reduce the attack surface.<\/li>\n<\/ul>\n\n\n\n<p>Proactively managing trunk ports and VLAN configurations is essential for maintaining network security.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Learn how VLAN tagging works, trunk configurations, and security tips for keeping networks safe.<\/p>\n","protected":false},"author":159,"featured_media":0,"template":"","funnel_stage":[3016],"coauthors":[2580],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v22.9 (Yoast SEO v22.9) - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>What Is VLAN Trunking? - JumpCloud<\/title>\n<meta name=\"description\" content=\"Learn how VLAN tagging works, trunk configurations, and security tips for keeping networks safe.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/jumpcloud.com\/it-index\/what-is-vlan-trunking\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"What Is VLAN Trunking?\" \/>\n<meta property=\"og:description\" content=\"Learn how VLAN tagging works, trunk configurations, and security tips for keeping networks safe.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/jumpcloud.com\/it-index\/what-is-vlan-trunking\" \/>\n<meta property=\"og:site_name\" content=\"JumpCloud\" \/>\n<meta property=\"article:modified_time\" content=\"2025-01-15T17:35:41+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/jumpcloud.com\/wp-content\/uploads\/2023\/01\/jumpcloud-logo-2023.png\" \/>\n\t<meta property=\"og:image:width\" content=\"1200\" \/>\n\t<meta property=\"og:image:height\" content=\"627\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/png\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data1\" content=\"4 minutes\" \/>\n\t<meta name=\"twitter:label2\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data2\" content=\"michael.cooley\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\/\/jumpcloud.com\/it-index\/what-is-vlan-trunking\",\"url\":\"https:\/\/jumpcloud.com\/it-index\/what-is-vlan-trunking\",\"name\":\"What Is VLAN Trunking? - JumpCloud\",\"isPartOf\":{\"@id\":\"https:\/\/jumpcloud.com\/#website\"},\"datePublished\":\"2025-01-07T19:06:10+00:00\",\"dateModified\":\"2025-01-15T17:35:41+00:00\",\"description\":\"Learn how VLAN tagging works, trunk configurations, and security tips for keeping networks safe.\",\"breadcrumb\":{\"@id\":\"https:\/\/jumpcloud.com\/it-index\/what-is-vlan-trunking#breadcrumb\"},\"inLanguage\":\"en-US\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\/\/jumpcloud.com\/it-index\/what-is-vlan-trunking\"]}]},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\/\/jumpcloud.com\/it-index\/what-is-vlan-trunking#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\/\/jumpcloud.com\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"IT Index\",\"item\":\"https:\/\/jumpcloud.com\/it-index\"},{\"@type\":\"ListItem\",\"position\":3,\"name\":\"What Is VLAN Trunking?\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\/\/jumpcloud.com\/#website\",\"url\":\"https:\/\/jumpcloud.com\/\",\"name\":\"JumpCloud\",\"description\":\"Daily insights on directory services, IAM, LDAP, identity security, SSO, system management (Mac, Windows, Linux), networking, and the cloud.\",\"publisher\":{\"@id\":\"https:\/\/jumpcloud.com\/#organization\"},\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\/\/jumpcloud.com\/?s={search_term_string}\"},\"query-input\":\"required name=search_term_string\"}],\"inLanguage\":\"en-US\"},{\"@type\":\"Organization\",\"@id\":\"https:\/\/jumpcloud.com\/#organization\",\"name\":\"JumpCloud\",\"url\":\"https:\/\/jumpcloud.com\/\",\"logo\":{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\/\/jumpcloud.com\/#\/schema\/logo\/image\/\",\"url\":\"https:\/\/jumpcloud.com\/wp-content\/uploads\/2021\/01\/jc-logo-brand-2021.png\",\"contentUrl\":\"https:\/\/jumpcloud.com\/wp-content\/uploads\/2021\/01\/jc-logo-brand-2021.png\",\"width\":598,\"height\":101,\"caption\":\"JumpCloud\"},\"image\":{\"@id\":\"https:\/\/jumpcloud.com\/#\/schema\/logo\/image\/\"}}]}<\/script>\n<!-- \/ Yoast SEO Premium plugin. -->","yoast_head_json":{"title":"What Is VLAN Trunking? - JumpCloud","description":"Learn how VLAN tagging works, trunk configurations, and security tips for keeping networks safe.","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/jumpcloud.com\/it-index\/what-is-vlan-trunking","og_locale":"en_US","og_type":"article","og_title":"What Is VLAN Trunking?","og_description":"Learn how VLAN tagging works, trunk configurations, and security tips for keeping networks safe.","og_url":"https:\/\/jumpcloud.com\/it-index\/what-is-vlan-trunking","og_site_name":"JumpCloud","article_modified_time":"2025-01-15T17:35:41+00:00","og_image":[{"width":1200,"height":627,"url":"https:\/\/jumpcloud.com\/wp-content\/uploads\/2023\/01\/jumpcloud-logo-2023.png","type":"image\/png"}],"twitter_card":"summary_large_image","twitter_misc":{"Est. reading time":"4 minutes","Written by":"michael.cooley"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"WebPage","@id":"https:\/\/jumpcloud.com\/it-index\/what-is-vlan-trunking","url":"https:\/\/jumpcloud.com\/it-index\/what-is-vlan-trunking","name":"What Is VLAN Trunking? - JumpCloud","isPartOf":{"@id":"https:\/\/jumpcloud.com\/#website"},"datePublished":"2025-01-07T19:06:10+00:00","dateModified":"2025-01-15T17:35:41+00:00","description":"Learn how VLAN tagging works, trunk configurations, and security tips for keeping networks safe.","breadcrumb":{"@id":"https:\/\/jumpcloud.com\/it-index\/what-is-vlan-trunking#breadcrumb"},"inLanguage":"en-US","potentialAction":[{"@type":"ReadAction","target":["https:\/\/jumpcloud.com\/it-index\/what-is-vlan-trunking"]}]},{"@type":"BreadcrumbList","@id":"https:\/\/jumpcloud.com\/it-index\/what-is-vlan-trunking#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/jumpcloud.com\/"},{"@type":"ListItem","position":2,"name":"IT Index","item":"https:\/\/jumpcloud.com\/it-index"},{"@type":"ListItem","position":3,"name":"What Is VLAN Trunking?"}]},{"@type":"WebSite","@id":"https:\/\/jumpcloud.com\/#website","url":"https:\/\/jumpcloud.com\/","name":"JumpCloud","description":"Daily insights on directory services, IAM, LDAP, identity security, SSO, system management (Mac, Windows, Linux), networking, and the cloud.","publisher":{"@id":"https:\/\/jumpcloud.com\/#organization"},"potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/jumpcloud.com\/?s={search_term_string}"},"query-input":"required name=search_term_string"}],"inLanguage":"en-US"},{"@type":"Organization","@id":"https:\/\/jumpcloud.com\/#organization","name":"JumpCloud","url":"https:\/\/jumpcloud.com\/","logo":{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/jumpcloud.com\/#\/schema\/logo\/image\/","url":"https:\/\/jumpcloud.com\/wp-content\/uploads\/2021\/01\/jc-logo-brand-2021.png","contentUrl":"https:\/\/jumpcloud.com\/wp-content\/uploads\/2021\/01\/jc-logo-brand-2021.png","width":598,"height":101,"caption":"JumpCloud"},"image":{"@id":"https:\/\/jumpcloud.com\/#\/schema\/logo\/image\/"}}]}},"_links":{"self":[{"href":"https:\/\/jumpcloud.com\/wp-json\/wp\/v2\/it-index\/119457"}],"collection":[{"href":"https:\/\/jumpcloud.com\/wp-json\/wp\/v2\/it-index"}],"about":[{"href":"https:\/\/jumpcloud.com\/wp-json\/wp\/v2\/types\/it-index"}],"author":[{"embeddable":true,"href":"https:\/\/jumpcloud.com\/wp-json\/wp\/v2\/users\/159"}],"version-history":[{"count":2,"href":"https:\/\/jumpcloud.com\/wp-json\/wp\/v2\/it-index\/119457\/revisions"}],"predecessor-version":[{"id":120047,"href":"https:\/\/jumpcloud.com\/wp-json\/wp\/v2\/it-index\/119457\/revisions\/120047"}],"wp:attachment":[{"href":"https:\/\/jumpcloud.com\/wp-json\/wp\/v2\/media?parent=119457"}],"wp:term":[{"taxonomy":"funnel_stage","embeddable":true,"href":"https:\/\/jumpcloud.com\/wp-json\/wp\/v2\/funnel_stage?post=119457"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/jumpcloud.com\/wp-json\/wp\/v2\/coauthors?post=119457"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}