# FRRouting Claims IBGP Loopbacks Are Inaccessible

DevFeed: [FRRouting Claims IBGP Loopbacks Are Inaccessible](<https://devfeed.tech/articles/frrouting-claims-ibgp-loopbacks-are-inaccessible-10960.md>)

Original publisher: [Read original article](<https://blog.ipspace.net/2024/03/frr-ibgp-loopbacks/>)

Published: 2024-03-27T07:10:00Z

Content type: article

Language: en

Sources: [ipSpace.net blog](<https://devfeed.tech/sources/ipspace-net-blog.md>)

Topics: [networking](<https://devfeed.tech/topics/networking.md>), [IP routing](<https://devfeed.tech/topics/ip-routing.md>), [BGP](<https://devfeed.tech/topics/bgp.md>), [Networks](<https://devfeed.tech/topics/networks.md>), [Routing (disambiguation)](<https://devfeed.tech/topics/routing.md>), [systems](<https://devfeed.tech/topics/systems.md>)

Tags: [bgp](<https://devfeed.tech/tags/bgp.md>), [blog-post](<https://devfeed.tech/tags/blog-post.md>), [ip-routing](<https://devfeed.tech/tags/ip-routing.md>), [networking](<https://devfeed.tech/tags/networking.md>), [networks](<https://devfeed.tech/tags/networks.md>), [ospf](<https://devfeed.tech/tags/ospf.md>), [routing](<https://devfeed.tech/tags/routing.md>), [systems](<https://devfeed.tech/tags/systems.md>)

## AI overview

The article examines how FRRouting handles prefixes advertised through both OSPF and IBGP. In the described case, FRRouting places both routes in the IP routing table but rejects the IBGP route for a loopback prefix because it considers the BGP next hop inaccessible, possibly due to recursive routing prevention logic.

## Source excerpt

Last week, I explained the differences between FRRouting and more traditional networking operating systems in scenarios where OSPF and IBGP advertise the same prefix: Traditional networking operating systems enter only the OSPF route into the IP routing table. FRRouting enters OSPF and IBGP routes into the IP routing table. On all platforms I've tested, only the OSPF route gets into the forwarding table1. One could conclude that it's perfectly safe to advertise the same prefixes in OSPF and IBGP. The OSPF routes will be used within the autonomous system, and the IBGP routes will be propagated over EBGP to adjacent networks. Well, one would be surprised 🤦♂ Read more ...