BFD and BGP route installation in Kernel

[robergeandre]

Hi,

I am experiencing an issue with FRR versions 10.4.3 and 10.5.1 regarding BFD and kernel route installation.

When BFD loses connectivity for only a few seconds, it functions correctly: BFD detects the failure, and once connectivity is restored, it reinstalls the routes into the kernel as expected. However, if the BFD session stays down for an extended period 10 +/- secondes), the routes are never reinstalled in the kernel after the session recovers.

Despite both BGP and BFD showing as 'Up' in the FRR status, the kernel routing table remains empty but the route in FRR routing table are good.

Route is present in the frr routing table

show bgp ipv6
BGP table version is 9, local router ID is 10.10.0.98, vrf id 0
Default local pref 100, local AS 65114
Status codes: s suppressed, d damped, h history, u unsorted, * 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
::/0 fe80::223 0 0 65517 i
*> fd51:2050:2220::98/128
:: 0 32768 ?

But not in the kernel table

ip -6 r
fd51:2050:2220::98 dev host0 proto kernel metric 256 pref medium
fe80::/64 dev enp1s0f0 proto kernel metric 256 pref medium
fe80::/64 dev enp1s0f1 proto kernel metric 256 pref medium
fe80::/64 dev host0 proto kernel metric 256 pref medium

Both BGP and BFD are up ans running but the route never get installed in the kernel.

show show bgp neighbor fe80::223
BGP neighbor is fe80::223, remote AS 65517, local AS 65114, external link
Local Role: undefined
Remote Role: undefined
BGP version 4, remote router ID 10.10.0.27, local router ID 10.10.0.98
BGP state = Established, up for 00:23:52
Last read 00:00:03, Last write 00:00:22
Hold time is 90 seconds, keepalive interval is 30 seconds
Configured hold time is 180 seconds, keepalive interval is 60 seconds
Configured tcp-mss is 0, synced tcp-mss is 8192
Configured conditional advertisements interval is 60 seconds
Neighbor capabilities:
4 Byte AS: advertised and received
Extended Message: advertised
AddPath:
IPv4 Unicast: RX advertised
IPv6 Unicast: RX advertised
Paths-Limit:
IPv4 Unicast: advertised (0)
IPv6 Unicast: advertised (0)
Long-lived Graceful Restart: advertised and received
Address families by peer:
Route refresh: advertised and received
Enhanced Route Refresh: advertised
Address Family IPv4 Unicast: advertised
Address Family IPv6 Unicast: advertised and received
Hostname Capability: advertised (name: cadevmysql1,domain name: n/a) not received
Version Capability: not advertised not received
Link-Local Next Hop Capability: not advertised not received
Graceful Restart Capability: advertised and received
Remote Restart timer is 120 seconds
Address families by peer:
none
Graceful restart information:
End-of-RIB send: IPv6 Unicast
End-of-RIB received: IPv6 Unicast
Local GR Mode: Helper*
Remote GR Mode: Helper
R bit: False
N bit: True
Timers:
Configured Restart Time(sec): 120
Received Restart Time(sec): 120
Configured LLGR Stale Path Time(sec): 0
IPv4 Unicast:
F bit: False
End-of-RIB sent: No
End-of-RIB sent after update: No

BFD Peer:
peer fe80::223 local-address fe80::8 vrf default interface enp1s0f1
ID: 2096685367
Remote ID: 329
Active mode
Status: up
Uptime: 3 minute(s), 19 second(s)
Diagnostics: ok
Remote diagnostics: ok
Peer Type: dynamic
RTT min/avg/max: 0/0/0 usec
Local timers:
Detect-multiplier: 3
Receive interval: 300ms
Transmission interval: 300ms
Echo receive interval: 50ms
Echo transmission interval: disabled
Remote timers:
Detect-multiplier: 3
Receive interval: 300ms
Transmission interval: 300ms
Echo receive interval: disabled

Thank You

[donaldsharp]

What's the state of the actual rib? show ip route. What does bgp believe nexthop tracking looks like show bgp nexthop and show ip nht please