--- title: 802.1 Protocol Stack « ipSpace.net blog | daily.dev description: A structured breakdown of the IEEE 802.1/802.3 Ethernet protocol stack, explaining how physical and data link layers are subdivided into sublayers (RS, PCS,... canonical: https://daily.dev/posts/802-1-protocol-stack-ipspace-net-blog-0yxwlmz1s twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: 802.1 Protocol Stack « ipSpace.net blog | daily.dev og:description: A structured breakdown of the IEEE 802.1/802.3 Ethernet protocol stack, explaining how physical and data link layers are subdivided into sublayers (RS, PCS,... og:url: https://daily.dev/posts/802-1-protocol-stack-ipspace-net-blog-0yxwlmz1s og:image: https://api.daily.dev/og/posts/0yXWlMz1s.png og:image:alt: 802.1 Protocol Stack « ipSpace.net blog og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # 802.1 Protocol Stack « ipSpace.net blog **[ipSpace.net Blog](https://daily.dev/sources/ipspace)** · 4 min read · 0 upvotes · 0 comments ## Summary A structured breakdown of the IEEE 802.1/802.3 Ethernet protocol stack, explaining how physical and data link layers are subdivided into sublayers (RS, PCS, PMA, PMD for physical; LLC and MAC for data link). The post maps key protocols — LLDP, LACP, STP, SPB, VLAN encapsulation, DTP, VTP, MVRP — to their correct positions in the stack. It also covers Linux networking quirks: Linux models everything as a device (bonds, VLAN interfaces, bridges, VRFs), which allows combining them in ways that break interoperability — specifically, attaching VLAN interfaces to a bridge produces STP frames incompatible with PVST+/RPVST+. The fix is using a VLAN-aware Linux bridge to place VLANs above STP-enabled links. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### Why does attaching VLAN interfaces to a Linux bridge break interoperability with Cisco PVST+? Attaching VLAN interfaces to a Linux bridge creates a bridged VLAN with STP running inside VLAN encapsulation, which resembles PVST+ or RPVST+ but uses different frame formats — making it incompatible. To interoperate with standard equipment, you must use a VLAN-aware Linux bridge, which places VLANs on top of STP-enabled links rather than wrapping STP inside VLAN frames. _Engineers troubleshooting Linux bridge and Cisco switch interoperability track issues like this on daily.dev._ ### What is the correct protocol layering order for LACP, STP, and VLANs in an Ethernet network? LLDP and LACP operate directly on top of the MAC sublayer. STP and Shortest Path Bridging (SPB) sit above LACP, treating link aggregation groups as the logical links to block. VLAN encapsulation is layered above STP. Per-VLAN spanning tree protocols (PVST+, RPVST+) include VLAN encapsulation in their BPDUs, placing them above the VLAN layer. _Network engineers keeping up with protocol stack fundamentals find relevant deep-dives on daily.dev._ ## Similar posts on daily.dev - [Worth Reading: An Interactive Introduction to the STP « ipSpace.net blog](https://daily.dev/posts/worth-reading-an-interactive-introduction-to-the-stp-ipspace-net-blog-3qa1wi7c5) · ipSpace.net Blog · 0 upvotes · 0 comments - [Entire Linux Network stack diagram](https://daily.dev/posts/entire-linux-network-stack-diagram-zetamcksd) · Hacker News · 1 upvotes · 0 comments - [An interactive introduction to the spanning tree protocol](https://daily.dev/posts/an-interactive-introduction-to-the-spanning-tree-protocol-xluhkmjrm) · Lobsters · 1 upvotes · 0 comments --- [View this post on daily.dev](https://daily.dev/posts/802-1-protocol-stack-ipspace-net-blog-0yxwlmz1s) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"802.1 Protocol Stack « ipSpace.net blog","url":"https://daily.dev/posts/802-1-protocol-stack-ipspace-net-blog-0yxwlmz1s","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/802-1-protocol-stack-ipspace-net-blog-0yxwlmz1s"},"datePublished":"2026-08-11T08:51:53.700Z","dateModified":"2026-08-11T08:52:55.521Z","description":"A structured breakdown of the IEEE 802.1/802.3 Ethernet protocol stack, explaining how physical and data link layers are subdivided into sublayers (RS, PCS,...","image":"https://media.daily.dev/image/upload/s--ZrL_HSsR--/f_auto/v1722860399/public/Placeholder%2006","thumbnailUrl":"https://media.daily.dev/image/upload/s--ZrL_HSsR--/f_auto/v1722860399/public/Placeholder%2006","isAccessibleForFree":true,"articleSection":"ipSpace.net Blog","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"ipSpace.net Blog","logo":"https://media.daily.dev/image/upload/s--xS7E82MT--/f_auto,q_auto/v1786438303/logos/ipspace?_a=BAMAMicg0","url":"https://daily.dev/sources/ipspace"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/802-1-protocol-stack-ipspace-net-blog-0yxwlmz1s","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"","timeRequired":"PT4M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"ipSpace.net Blog","item":"https://daily.dev/sources/ipspace"},{"@type":"ListItem","position":3,"name":"802.1 Protocol Stack « ipSpace.net blog"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/802-1-protocol-stack-ipspace-net-blog-0yxwlmz1s#faq","mainEntity":[{"@type":"Question","name":"Why does attaching VLAN interfaces to a Linux bridge break interoperability with Cisco PVST+?","acceptedAnswer":{"@type":"Answer","text":"Attaching VLAN interfaces to a Linux bridge creates a bridged VLAN with STP running inside VLAN encapsulation, which resembles PVST+ or RPVST+ but uses different frame formats — making it incompatible. 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