--- title: VXLAN with IPv6 Next Hops « ipSpace.net blog | daily.dev description: FRRouting 10.6 introduced BGP IPv6 VTEP support for EVPN, but interoperability testing with Arista EOS (release 4.35.2F) revealed a bug: FRRouting's BGP daemon... canonical: https://daily.dev/posts/vxlan-with-ipv6-next-hops-ipspace-net-blog-nw3evvshj twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: VXLAN with IPv6 Next Hops « ipSpace.net blog | daily.dev og:description: FRRouting 10.6 introduced BGP IPv6 VTEP support for EVPN, but interoperability testing with Arista EOS (release 4.35.2F) revealed a bug: FRRouting's BGP daemon... og:url: https://daily.dev/posts/vxlan-with-ipv6-next-hops-ipspace-net-blog-nw3evvshj og:image: https://api.daily.dev/og/posts/NW3EVvShJ.png og:image:alt: VXLAN with IPv6 Next Hops « 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. # VXLAN with IPv6 Next Hops « ipSpace.net blog **[ipSpace.net Blog](https://daily.dev/sources/ipspace)** · 5 min read · 0 upvotes · 0 comments ## Summary FRRouting 10.6 introduced BGP IPv6 VTEP support for EVPN, but interoperability testing with Arista EOS (release 4.35.2F) revealed a bug: FRRouting's BGP daemon rejected EVPN IMET routes from Arista when both the next hop and the PMSI Tunnel ID were IPv6 addresses. The root cause is a difference in PMSI_TUNNEL_ATTRIBUTE encoding — Arista uses an IPv6 address as the Tunnel ID, while FRRouting uses 0.0.0.0 even with IPv6 VTEPs. Donald Sharp fixed the bug in under 48 hours via a GitHub PR. The post also explains the PMSI Tunnel attribute (RFC 6514), its role in BUM replication signaling for EVPN/VXLAN, and provides the full lab topology (using netlab with Arista cEOS and FRRouting containers) to reproduce the issue. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### Why does FRRouting reject EVPN IMET routes with IPv6 next hops from Arista EOS with 'Bad PMSI tunnel attribute length 21 for IR'? FRRouting rejects these routes because it does not accept an IPv6 address as the PMSI Tunnel ID in the PMSI_TUNNEL_ATTRIBUTE when running EVPN over IPv6. Arista EOS encodes the Tunnel ID as an IPv6 address (e.g., 2001:db8:0:1::1), while FRRouting expects 0.0.0.0 even with IPv6 VTEPs. This mismatch causes FRRouting's BGP daemon to treat the route as a withdrawal. The bug was fixed in FRRouting via PR #21488. _Engineers running multi-vendor EVPN labs track FRRouting interoperability fixes like this on daily.dev._ ### What does the PMSI Tunnel attribute do in EVPN/VXLAN and what RFC defines it? The PMSI Tunnel attribute, defined in RFC 6514 Section 5, is carried with IMET (type 3) EVPN routes to signal which BUM (Broadcast, Unknown unicast, Multicast) replication method a device uses. In EVPN/VXLAN environments, common values are type 3 or 4 for multicast replication and type 6 for ingress replication. The Tunnel ID field is variable-length, allowing both IPv4 and IPv6 addresses. _Networking engineers building EVPN/VXLAN labs find RFC deep-dives and interop reports like this on daily.dev._ ## Similar posts on daily.dev - [BGP-Free Network Core with SRv6 « ipSpace.net blog](https://daily.dev/posts/bgp-free-network-core-with-srv6-ipspace-net-blog-9bbn88wub) · ipSpace.net Blog · 0 upvotes · 0 comments - [The Never-Ending IPv6 Loopback Prefix Saga « ipSpace.net blog](https://daily.dev/posts/the-never-ending-ipv6-loopback-prefix-saga-ipspace-net-blog-4nlhgh10l) · ipSpace.net Blog · 0 upvotes · 0 comments - [Multivendor SR-MPLS « ipSpace.net blog](https://daily.dev/posts/multivendor-sr-mpls-ipspace-net-blog-qekokwduk) · ipSpace.net Blog · 0 upvotes · 0 comments - [EVPN with SR-MPLS Core « ipSpace.net blog](https://daily.dev/posts/evpn-with-sr-mpls-core-ipspace-net-blog-taobtibzc) · ipSpace.net Blog · 0 upvotes · 0 comments --- Tags: [#bgp](https://daily.dev/tags/bgp), [#evpn](https://daily.dev/tags/evpn) [View this post on daily.dev](https://daily.dev/posts/vxlan-with-ipv6-next-hops-ipspace-net-blog-nw3evvshj) ```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":"VXLAN with IPv6 Next Hops « ipSpace.net blog","url":"https://daily.dev/posts/vxlan-with-ipv6-next-hops-ipspace-net-blog-nw3evvshj","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/vxlan-with-ipv6-next-hops-ipspace-net-blog-nw3evvshj"},"datePublished":"2026-08-11T08:54:15.677Z","dateModified":"2026-08-24T07:09:00.039Z","description":"FRRouting 10.6 introduced BGP IPv6 VTEP support for EVPN, but interoperability testing with Arista EOS (release 4.35.2F) revealed a bug: FRRouting's BGP daemon...","image":"https://media.daily.dev/image/upload/s--foaA6JGU--/f_auto/v1722860399/public/Placeholder%2004","thumbnailUrl":"https://media.daily.dev/image/upload/s--foaA6JGU--/f_auto/v1722860399/public/Placeholder%2004","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/vxlan-with-ipv6-next-hops-ipspace-net-blog-nw3evvshj","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"bgp,evpn","timeRequired":"PT5M"} {"@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":"VXLAN with IPv6 Next Hops « ipSpace.net blog"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/vxlan-with-ipv6-next-hops-ipspace-net-blog-nw3evvshj#faq","mainEntity":[{"@type":"Question","name":"Why does FRRouting reject EVPN IMET routes with IPv6 next hops from Arista EOS with 'Bad PMSI tunnel attribute length 21 for IR'?","acceptedAnswer":{"@type":"Answer","text":"FRRouting rejects these routes because it does not accept an IPv6 address as the PMSI Tunnel ID in the PMSI_TUNNEL_ATTRIBUTE when running EVPN over IPv6. Arista EOS encodes the Tunnel ID as an IPv6 address (e.g., 2001:db8:0:1::1), while FRRouting expects 0.0.0.0 even with IPv6 VTEPs. This mismatch causes FRRouting's BGP daemon to treat the route as a withdrawal. The bug was fixed in FRRouting via PR #21488. Engineers running multi-vendor EVPN labs track FRRouting interoperability fixes like this on daily.dev."}},{"@type":"Question","name":"What does the PMSI Tunnel attribute do in EVPN/VXLAN and what RFC defines it?","acceptedAnswer":{"@type":"Answer","text":"The PMSI Tunnel attribute, defined in RFC 6514 Section 5, is carried with IMET (type 3) EVPN routes to signal which BUM (Broadcast, Unknown unicast, Multicast) replication method a device uses. In EVPN/VXLAN environments, common values are type 3 or 4 for multicast replication and type 6 for ingress replication. The Tunnel ID field is variable-length, allowing both IPv4 and IPv6 addresses. 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