--- title: Dual-Stack SR-MPLS « ipSpace.net blog | daily.dev description: A hands-on walkthrough of configuring dual-stack SR-MPLS using netlab, demonstrating how node segment identifiers (SIDs) can be assigned to both IPv4 and IPv6... canonical: https://daily.dev/posts/dual-stack-sr-mpls-ipspace-net-blog-nkkvmbn0t twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Dual-Stack SR-MPLS « ipSpace.net blog | daily.dev og:description: A hands-on walkthrough of configuring dual-stack SR-MPLS using netlab, demonstrating how node segment identifiers (SIDs) can be assigned to both IPv4 and IPv6... og:url: https://daily.dev/posts/dual-stack-sr-mpls-ipspace-net-blog-nkkvmbn0t og:image: https://api.daily.dev/og/posts/NKkvMBN0t.png og:image:alt: Dual-Stack SR-MPLS « 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. # Dual-Stack SR-MPLS « ipSpace.net blog **[ipSpace.net Blog](https://daily.dev/sources/ipspace)** · 7 min read · 0 upvotes · 0 comments ## Summary A hands-on walkthrough of configuring dual-stack SR-MPLS using netlab, demonstrating how node segment identifiers (SIDs) can be assigned to both IPv4 and IPv6 prefixes in a three-router IS-IS topology. The post covers lab topology setup with custom address pools, IS-IS LSP TLV verification, MPLS forwarding table inspection, and a critical gotcha: Arista EOS and Cisco IOS XR only advertise SR-MPLS SID sub-TLVs for IPv6 loopback prefixes when they are /128 — not /64 — while Cisco IOS XE cannot assign SIDs to IPv6 prefixes at all. FRRouting, Junos, and Nokia SR Linux handle /64 loopbacks without issue. The lab is available as a GitHub Codespace using Arista cEOS containers. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### Why is Arista EOS not advertising SR-MPLS SID for my IPv6 loopback prefix in IS-IS? Arista EOS (and Cisco IOS XR) only advertise the SR-MPLS SID sub-TLV for an IPv6 loopback prefix when that prefix is a /128. If the loopback is configured as a /64, no SID is advertised in IS-IS — and neither platform generates an obvious error message. Cisco IOS XR makes it worse by assigning the MPLS label locally but silently omitting the IS-IS advertisement. _Engineers troubleshooting SR-MPLS IPv6 SID visibility across vendors find the relevant gotchas on daily.dev._ ### Can Cisco IOS XE assign SR-MPLS segment IDs to IPv6 prefixes? Cisco IOS XE cannot assign SIDs to IPv6 prefixes in SR-MPLS. Among tested platforms, FRRouting, Junos, Nokia SR Linux, Arista EOS, and Cisco IOS XR all support dual-stack SR-MPLS node SIDs, but IOS XE is the exception and supports only IPv4 SIDs. _Keeping track of per-vendor SR-MPLS feature gaps is easier when the networking community's findings are aggregated in one place like daily.dev._ ## Similar posts on daily.dev - [Multivendor SR-MPLS « ipSpace.net blog](https://daily.dev/posts/multivendor-sr-mpls-ipspace-net-blog-qekokwduk) · ipSpace.net Blog · 0 upvotes · 0 comments - [MPLS/VPN with SR-MPLS Core « ipSpace.net blog](https://daily.dev/posts/mpls-vpn-with-sr-mpls-core-ipspace-net-blog-nw3uwiphe) · ipSpace.net Blog · 0 upvotes · 0 comments - [BGP-Free Core with SR-MPLS « ipSpace.net blog](https://daily.dev/posts/bgp-free-core-with-sr-mpls-ipspace-net-blog-h7kronzy3) · 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 - [Configuring SRv6 on Junos \(Locator and IGP\) « ipSpace.net blog](https://daily.dev/posts/configuring-srv6-on-junos-locator-and-igp-ipspace-net-blog-bhavnkj81) · ipSpace.net Blog · 0 upvotes · 0 comments --- Tags: [#networking](https://daily.dev/tags/networking) [View this post on daily.dev](https://daily.dev/posts/dual-stack-sr-mpls-ipspace-net-blog-nkkvmbn0t) ```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":"Dual-Stack SR-MPLS « ipSpace.net blog","url":"https://daily.dev/posts/dual-stack-sr-mpls-ipspace-net-blog-nkkvmbn0t","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/dual-stack-sr-mpls-ipspace-net-blog-nkkvmbn0t"},"datePublished":"2026-08-11T08:54:30.594Z","dateModified":"2026-08-24T06:58:51.890Z","description":"A hands-on walkthrough of configuring dual-stack SR-MPLS using netlab, demonstrating how node segment identifiers (SIDs) can be assigned to both IPv4 and IPv6...","image":"https://media.daily.dev/image/upload/s--1KxV4ohY--/f_auto/v1722860400/public/Placeholder%2007","thumbnailUrl":"https://media.daily.dev/image/upload/s--1KxV4ohY--/f_auto/v1722860400/public/Placeholder%2007","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/dual-stack-sr-mpls-ipspace-net-blog-nkkvmbn0t","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"networking","timeRequired":"PT7M"} {"@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":"Dual-Stack SR-MPLS « ipSpace.net blog"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/dual-stack-sr-mpls-ipspace-net-blog-nkkvmbn0t#faq","mainEntity":[{"@type":"Question","name":"Why is Arista EOS not advertising SR-MPLS SID for my IPv6 loopback prefix in IS-IS?","acceptedAnswer":{"@type":"Answer","text":"Arista EOS (and Cisco IOS XR) only advertise the SR-MPLS SID sub-TLV for an IPv6 loopback prefix when that prefix is a /128. 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