--- title: FRRouting Claims IBGP Loopbacks Are Inaccessible «... description: FRRouting exhibits unexpected behavior when OSPF and IBGP advertise the same prefix (e.g., a loopback address). While the OSPF route is correctly installed in... canonical: https://daily.dev/posts/frrouting-claims-ibgp-loopbacks-are-inaccessible-ipspace-net-blog-0gh7oazxl twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: FRRouting Claims IBGP Loopbacks Are Inaccessible « ipSpace.net blog | daily.dev og:description: FRRouting exhibits unexpected behavior when OSPF and IBGP advertise the same prefix (e.g., a loopback address). While the OSPF route is correctly installed in... og:url: https://daily.dev/posts/frrouting-claims-ibgp-loopbacks-are-inaccessible-ipspace-net-blog-0gh7oazxl og:image: https://api.daily.dev/og/posts/0GH7oazxL.png og:image:alt: FRRouting Claims IBGP Loopbacks Are Inaccessible « 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. # FRRouting Claims IBGP Loopbacks Are Inaccessible « ipSpace.net blog **[ipSpace.net Blog](https://daily.dev/sources/ipspace)** · 6 min read · 0 upvotes · 0 comments ## Summary FRRouting exhibits unexpected behavior when OSPF and IBGP advertise the same prefix (e.g., a loopback address). While the OSPF route is correctly installed in the forwarding table, FRRouting marks the IBGP route for that loopback as invalid due to an 'inaccessible' next hop — even though the next hop is reachable via OSPF in the routing table. The likely cause is overly aggressive recursive routing prevention logic: FRRouting appears to reject the IBGP route because its next hop matches the prefix itself, without properly distinguishing that the best route for that prefix is an OSPF route, not the IBGP route. The author suspects this behavior was introduced to handle edge cases in EVPN IBGP-over-EBGP designs, at the cost of breaking otherwise valid configurations. ## 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 mark an IBGP route as inaccessible even though the next hop is reachable via OSPF? FRRouting's recursive routing prevention logic appears to reject an IBGP route when its next hop IP matches the advertised prefix itself, without checking whether the best route for that prefix is an IGP route rather than the IBGP route. The OSPF route for the loopback is present and selected in the forwarding table, but FRRouting still flags the IBGP next hop as inaccessible and marks the route invalid. _Engineers debugging FRRouting BGP behavior track issues like this on daily.dev before spending hours in the source code._ ### Does FRRouting advertise IBGP routes even when OSPF has a better route for the same prefix? FRRouting enters both OSPF and IBGP routes into the IP routing table when they advertise the same prefix, but only the OSPF route reaches the forwarding table. Unlike traditional networking OSes that keep only the OSPF route in the routing table, FRRouting keeps both — yet still refuses to select the IBGP route as best when the next hop matches the prefix, marking it invalid. _Network engineers comparing FRRouting to traditional NOS behavior find edge cases like this discussed on daily.dev._ ## Similar posts on daily.dev - [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 - [RFC8950: Announce IPv4 with an IPv6 next-hop](https://daily.dev/posts/rfc8950-announce-ipv4-with-an-ipv6-next-hop-p51bkdm9a) · Hacker News · 0 upvotes · 0 comments - [Dear Junos, Tunnels Are Not Virtual Links « ipSpace.net blog](https://daily.dev/posts/dear-junos-tunnels-are-not-virtual-links-ipspace-net-blog-1zdexbued) · ipSpace.net Blog · 0 upvotes · 0 comments --- Tags: [#bgp](https://daily.dev/tags/bgp) [View this post on daily.dev](https://daily.dev/posts/frrouting-claims-ibgp-loopbacks-are-inaccessible-ipspace-net-blog-0gh7oazxl) ```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":"FRRouting Claims IBGP Loopbacks Are Inaccessible « ipSpace.net blog","url":"https://daily.dev/posts/frrouting-claims-ibgp-loopbacks-are-inaccessible-ipspace-net-blog-0gh7oazxl","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/frrouting-claims-ibgp-loopbacks-are-inaccessible-ipspace-net-blog-0gh7oazxl"},"datePublished":"2026-08-11T08:55:07.932Z","dateModified":"2026-08-24T06:58:48.995Z","description":"FRRouting exhibits unexpected behavior when OSPF and IBGP advertise the same prefix (e.g., a loopback address). 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