Hi - I noticed that after upgrading a few of my boxes to FRR 8, link prefixes are no longer advertised in BGP. I tracked it down to this commit: https://github.com/FRRouting/frr/commit/654a5978f695087af062bfc9a382321fa2cc... More info: I run EBGP w/ FRR over a few P-t-P OpenVPN tunnels that are configured similar to the following: (dax:23:35:EDT)% ifconfig tun0 tun0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> metric 0 mtu 1414 options=80000<LINKSTATE> inet 10.3.254.11 --> 10.3.254.12 netmask 0xffffffff inet6 2620:6:2000:1ff::1181 prefixlen 124 inet6 fe80::202:bcff:fe56:cb39%tun0 prefixlen 64 scopeid 0x11 groups: tun nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL> Opened by PID 53497 Each side of the link is configured as a /32. I have network statements in FRR so that each side advertises its own /32 on the link, to allow applications that don't bind to the loopback to work properly. This has worked fine up until FRR 8 on both FreeBSD & Linux. For example, peer 10.3.254.83 is advertising 10.3.254.83/32 and it's being accepted: nox# show ip bgp nei 10.3.254.83 routes BGP table version is 70477, local router ID is 10.3.4.20, vrf id 0 Default local pref 100, local AS 65307 Status codes: s suppressed, d damped, h history, * valid, > best, = multipath, i internal, r RIB-failure, S Stale, R Removed Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self Origin codes: i - IGP, e - EGP, ? - incomplete Network Next Hop Metric LocPrf Weight Path *> 10.3.4.18/32 10.3.254.83 0 65306 i *> 10.3.254.36/32 10.3.254.83 0 65306 i *> 10.3.254.83/32 10.3.254.83 0 65306 i Displayed 3 routes and 1222 total paths nox# show ip bgp 10.3.254.83/32 BGP routing table entry for 10.3.254.83/32 Paths: (2 available, best #2, table default) Advertised to non peer-group peers: 10.3.254.5 10.3.254.9 10.3.254.21 10.3.254.40 10.3.254.44 10.3.254.73 10.3.254.83 10.3.254.85 10.3.254.94 10.3.254.113 10.3.254.164 10.3.254.179 65304 65306 10.3.254.21 from 10.3.254.21 (10.3.4.6) Origin IGP, valid, external Last update: Sun Aug 28 22:17:11 2022 65306 10.3.254.83 from 10.3.254.83 (10.3.4.18) Origin IGP, valid, external, best (AS Path) Last update: Sun Aug 28 10:29:03 2022 However, in FRR 8, this no longer works due to the commit above. Example for 10.3.254.12 advertising 10.3.254.12/32: dax.prolixium.com# show ip bgp neighbors 10.3.254.12 routes BGP table version is 280, local router ID is 10.3.4.6, vrf id 0 Default local pref 100, local AS 65304 Status codes: s suppressed, d damped, h history, * valid, > best, = multipath, i internal, r RIB-failure, S Stale, R Removed Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self Origin codes: i - IGP, e - EGP, ? - incomplete RPKI validation codes: V valid, I invalid, N Not found Network Next Hop Metric LocPrf Weight Path *> 10.3.4.25/32 10.3.254.12 0 0 65307 i 10.3.254.12/32 10.3.254.12 0 0 65307 i Displayed 2 routes and 1212 total paths dax.prolixium.com# show ip bgp 10.3.254.12/32 BGP routing table entry for 10.3.254.12/32, version 278 Paths: (2 available, best #2, table default) Advertised to non peer-group peers: 10.3.4.35 10.3.7.238 10.3.254.4 10.3.254.12 10.3.254.14 10.3.254.20 10.3.254.23 10.3.254.36 10.3.254.67 10.3.254.81 10.3.254.115 10.3.254.122 10.3.254.161 65307 10.3.254.12 (inaccessible) from 10.3.254.12 (10.3.4.25) Origin IGP, metric 0, invalid, external Last update: Sun Aug 28 23:42:58 2022 Local 0.0.0.0 from 0.0.0.0 (10.3.4.6) Origin IGP, metric 0, weight 32768, valid, sourced, local, best (First path received) Last update: Sun Aug 28 23:23:21 2022 dax.prolixium.com# When turning up debugs, this is clearly seen in the logs: 2022/08/28 23:06:47 BGP: [T5AAP-5GA85] 10.3.254.12(trance_bgpd) rcvd UPDATE w/ attr: nexthop 10.3.254.12, origin i, metric 0, path 65307 2022/08/28 23:06:47 BGP: [PCFFM-WMARW] 10.3.254.12(trance_bgpd) rcvd UPDATE wlen 0 attrlen 28 alen 10 2022/08/28 23:06:47 BGP: [YCKEM-GB33T] 10.3.254.12(trance_bgpd) rcvd 10.3.4.25/32 IPv4 unicast 2022/08/28 23:06:47 BGP: [J47J0-K06GG] Found existing bnc 10.3.254.12/32(VRF default) flags 0xf ifindex 0 #paths 0 peer 0x82fb50740 2022/08/28 23:06:47 BGP: [YCKEM-GB33T] 10.3.254.12(trance_bgpd) rcvd 10.3.254.12/32 IPv4 unicast 2022/08/28 23:06:47 BGP: [N1KDM-HR02D] bgp_find_or_add_nexthop(10.3.254.12/32): prefix loops through itself 2022/08/28 23:06:47 BGP: [YT4EY-7V2YV] bgp_update(10.3.254.12): NH unresolved Are there workarounds for this or is this capability something that FRR has intentionally dropped permanently (and I should renumber my tunnels..)? Thanks! - Mark -- Mark Kamichoff prox@prolixium.com https://www.prolixium.com/