--- title: Design Clinic: Small-Site IPv6 Multihoming « ipSpace.net... description: Small and medium enterprises using multiple ISPs face a persistent unsolved problem with IPv6 multihoming when they lack Provider Independent (PI) address... canonical: https://daily.dev/posts/design-clinic-small-site-ipv6-multihoming-ipspace-net-blog-u9t6brezt twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Design Clinic: Small-Site IPv6 Multihoming « ipSpace.net blog | daily.dev og:description: Small and medium enterprises using multiple ISPs face a persistent unsolved problem with IPv6 multihoming when they lack Provider Independent (PI) address... og:url: https://daily.dev/posts/design-clinic-small-site-ipv6-multihoming-ipspace-net-blog-u9t6brezt og:image: https://api.daily.dev/og/posts/U9T6brEzT.png og:image:alt: Design Clinic: Small-Site IPv6 Multihoming « 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. # Design Clinic: Small-Site IPv6 Multihoming « ipSpace.net blog **[ipSpace.net Blog](https://daily.dev/sources/ipspace)** · 2 min read · 0 upvotes · 0 comments ## Summary Small and medium enterprises using multiple ISPs face a persistent unsolved problem with IPv6 multihoming when they lack Provider Independent (PI) address space. Despite numerous RFCs addressing host source address selection, first-hop router selection, and prefix advertisement, no widely implemented solution exists. NPT66 (Network Prefix Translation) remains the most practical workaround, though it conflicts with IPv6's end-to-end design philosophy. ULA (Unique Local Addresses) as internal addressing has its own pitfalls. The discussion explores real-world options including NPT66 toward a backup ISP, modifying host address selection policies, and vendor-specific implementation quirks such as IOS-XE 16.x limiting NPTv6 to a single external prefix globally. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### How do I do IPv6 multihoming with multiple ISPs if I don't have my own Provider Independent IPv6 space? No widely implemented clean solution exists. The most practical approach is NPT66 (Network Prefix Translation): use one ISP's delegated prefix as your internal address space and apply NPT66 toward the backup ISP. Alternatively, modify host IPv6 source address selection policy (e.g., via /etc/gai.conf on Linux or netsh on Windows) when using ULA internally. RFC 8678 acknowledges the problem remains unsolved without some form of NAT. _Network engineers navigating multi-ISP IPv6 deployments track evolving workarounds and RFC discussions on daily.dev._ ### What are the limitations of NPTv6 in Cisco IOS-XE for small site multihoming? In IOS-XE 16.x, NPTv6 only supports translating an internal ULA prefix to a single external GUA prefix globally, making it unusable for true multi-ISP multihoming without adding dedicated hardware per circuit. The implementation may also break IPv6 traceroute. Simple reflexive ACLs are unsupported, forcing use of Zone-Based Firewall. VyOS/Vyatta reportedly offers a more flexible NPTv6 implementation. _Engineers evaluating router platforms for IPv6 multihoming find vendor comparison threads like this on daily.dev._ ## Similar posts on daily.dev - [UDP Broadcasting And The Brave New World Of IPv6](https://daily.dev/posts/udp-broadcasting-and-the-brave-new-world-of-ipv6-kbr2qsudb) · Hackaday · 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 - [I spent a WEEK without IPv4 to understand IPv6 transition mechanisms](https://daily.dev/posts/i-spent-a-week-without-ipv4-to-understand-ipv6-transition-mechanisms-iscykz0il) · Hacker News · 2 upvotes · 0 comments - [misc/why6why.md at main · becarpenter/misc](https://daily.dev/posts/misc-why6why-md-at-main-becarpenter-misc-vdnnmpiyy) · Lobsters · 0 upvotes · 0 comments --- Tags: [#bgp](https://daily.dev/tags/bgp) [View this post on daily.dev](https://daily.dev/posts/design-clinic-small-site-ipv6-multihoming-ipspace-net-blog-u9t6brezt) ```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":"Design Clinic: Small-Site IPv6 Multihoming « ipSpace.net blog","url":"https://daily.dev/posts/design-clinic-small-site-ipv6-multihoming-ipspace-net-blog-u9t6brezt","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/design-clinic-small-site-ipv6-multihoming-ipspace-net-blog-u9t6brezt"},"datePublished":"2026-08-11T08:56:05.339Z","dateModified":"2026-08-11T09:30:27.474Z","description":"Small and medium enterprises using multiple ISPs face a persistent unsolved problem with IPv6 multihoming when they lack Provider Independent (PI) address...","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/design-clinic-small-site-ipv6-multihoming-ipspace-net-blog-u9t6brezt","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"bgp","timeRequired":"PT2M"} {"@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":"Design Clinic: Small-Site IPv6 Multihoming « ipSpace.net blog"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/design-clinic-small-site-ipv6-multihoming-ipspace-net-blog-u9t6brezt#faq","mainEntity":[{"@type":"Question","name":"How do I do IPv6 multihoming with multiple ISPs if I don't have my own Provider Independent IPv6 space?","acceptedAnswer":{"@type":"Answer","text":"No widely implemented clean solution exists. 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