Symptom

1). Configuring a ipv6 bgp neighbor fails if that address is configured on a local interface but different VRF. interface port-channel81.220 description blah mtu 9100 encapsulation dot1q 220 bfd interval 300 min_rx 300 multiplier 3 no ip redirects ip address 172.16.101.193/31 ipv6 address 2600:300:2040:75::1/64 no shutdown N9K(config)# router bgp 64777 N9K(config-router)# vrf GN_VRF N9K(config-router-vrf)# N9K(config-router-vrf)# neighbor 2600:300:2040:75::1 Cannot give local interface address as neighbor 2). If ipv6 bgp neighbor is configured first and then a local interface in a different vrf is assigned the same IP address, config succeeds. However, all route updates from the neighbor fail, rejected as attribute fails as seen in 'debug bgp updates'. show bgp vrf all all neighbors shows several updates received but zero accepted. BGP neighbor is 2600:300:2040:75::1, remote AS 64777, ebgp link, Peer index 5 Description: CONCA401MOS_GN_VRF BGP version 4, remote router ID 10.83.165.253 BGP state = Established, up for 01:09:02 Peer is directly attached, interface port-channel11.202 BFD live-detection is configured and enabled, state is Up Private AS numbers removed from updates sent to this neighbor Last read 00:00:28, hold time = 90, keepalive interval is 30 seconds Last written 00:00:29, keepalive timer expiry due 0.111138 Received 2352 messages, 0 notifications, 0 bytes in queue Sent 646 messages, 0 notifications, 0 bytes in queue Connections established 3, dropped 2 Last reset by peer 01:09:50, due to session closed Last reset by us never, due to No error Neighbor capabilities: Dynamic capability: advertised (mp, refresh, gr) Dynamic capability (old): advertised Route refresh capability (new): advertised received Route refresh capability (old): advertised received 4-Byte AS capability: advertised received Address family IPv6 Unicast: advertised received Graceful Restart capability: advertised received Graceful Restart Parameters: Address families advertised to peer: IPv6 Unicast Address families received from peer: IPv6 Unicast Forwarding state preserved by peer for: Restart time advertised to peer: 120 seconds Stale time for routes advertised by peer: 300 seconds Restart time advertised by peer: 120 seconds Extended Next Hop Encoding Capability: advertised Message statistics: Sent Rcvd Opens: 3 3 Notifications: 0 0 Updates: 171 1920 <<================ Keepalives: 472 429 Route Refresh: 0 0 Capability: 0 0 Total: 646 2352 Total bytes: 28677 443992 Bytes in queue: 0 0 For address family: IPv6 Unicast BGP table version 2069, neighbor version 2069 0 accepted paths consume 0 bytes of memory <<============== 46 sent paths Community attribute sent to this neighbor Extended community attribute sent to this neighbor Inbound route-map configured is V6_GN_MIPE_IN, handle obtained Outbound route-map configured is V6_GN_MIPE_OUT, handle obtained Last End-of-RIB received 00:00:05 after session start Local host: 2600:300:2040:75::2, Local port: 179 Foreign host: 2600:300:2040:75::1, Foreign port: 41316 fd = 120 debug bgp updates: 2020 Dec 8 19:50:04.901660 bgp: 20057 [10564] (Gn) UPD: Received UPDATE message from 2600:300:2040:75::1 2020 Dec 8 19:50:04.901797 bgp: 20057 [10564] (Gn) UPD: Peer 2600:300:2040:75::1 advertised our address (2600:300:2040:75::1) as nexthop, dropping NLRI <<================= 2020 Dec 8 19:50:04.901945 bgp: 20057 [10564] (Gn) UPD: [IPv6 Unicast] Received prefix 2001:1890:fc:1897::/64 from peer 2600:300:2040:75::1, origin 2, next hop ::ffff:0.0.0.0, localpref 0, med 0 2020 Dec 8 19:50:04.901977 bgp: 20057 [10564] (Gn) UPD: [IPv6 Unicast] Dropping prefix 2001:1890:fc:1897::/64 from peer 2600:300:2040:75::1, due to attribute error <<================ 2020 Dec 8 19:50:04.902012 bgp: 20057 [10564] (Gn) UPD: [IPv6 Unicast] Received prefix 2001:1890:fc:1896::/64 from peer 2600:300:2040:75::1, origin 2, next hop ::ffff:0.0.0.0, localpref 0, med 0 2020 Dec 8 19:50:04.902043 bgp: 20057 [10564] (Gn) UPD: [IPv6 Unicast] Dropping prefix 2001:1890:fc:1896::/64 from peer 2600:300:2040:75::1, due to attribute error 2020 Dec 8 19:50:04.902069 bgp: librpm 20057 [10564] rpm_bgp_delete_from_attr_cache() - attr: 0x69bf248c 2020 Dec 8 19:50:04.902093 bgp: 20057 [10564] (Gn) UPD: Received UPDATE message from 2600:300:2040:75::1

Conditions

local interface ipv6 address configured in a VRF is used/configured as bgp neighbor in a different vrf

Workaround

reconfigure ipv6 addresses and eliminate conflict.

Further Problem Description