BGP Multihome Failover

[dstout89]

I'm working on a lab to setup a BGP multihome configuration and running into an issue with the failover while testing ssh and killing one of the routers.

Router A (AS10) -------- Router B (AS1000) -------- Router D (AS20)
                        \                                                      /
                          -------- Router C (AS2000) --------

Router A is able to see the network advertised by D via B and C correctly. The routes are additionally set to ECMP. If I do a traceroute from a client in AS10 to a client in AS20, I'll see whichever interfaces are currently set as the preferred route in the BGP routing table (for this we'll say it is currently going over B). If I disable router B and run traceroute again, I can see the route has automatically shifted to C correctly.

Now lets assume everything is reset and the preferred route is on B again. I can open an SSH connection to the client in AS20 and verify the traffic is going through B. If I disable B, the connection hangs and I can see it is still attempting to send traffic over the A -- B link. If I kill the SSH session and restart it, the traffic goes over C correctly.

Should the failover work while the SSH session is active so that my traffic is automatically rerouted through C, is this expected behavior, or is there a configuration I'm missing?

Router A BGP configuration:
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Note: 1.1.1.1 = Router B; 3.3.3.1 Router C; prefix-lists/route-maps are set to 'any'
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frr version 8.5.4
frr defaults traditional
hostname OPNsense.localdomain
log syslog notifications
!
router bgp 10
 bgp log-neighbor-changes
 no bgp ebgp-requires-policy
 no bgp default ipv4-unicast
 bgp bestpath as-path multipath-relax
 neighbor 1.1.1.1 remote-as 1000
 neighbor 1.1.1.1 update-source em0
 neighbor 3.3.3.1 remote-as 2000
 neighbor 3.3.3.1 update-source em2
 !
 address-family ipv4 unicast
  network 172.16.100.0/24
  neighbor 1.1.1.1 activate
  neighbor 1.1.1.1 prefix-list Allow in
  neighbor 1.1.1.1 prefix-list Allow out
  neighbor 1.1.1.1 route-map Allow in
  neighbor 1.1.1.1 route-map Allow out
  neighbor 3.3.3.1 activate
  neighbor 3.3.3.1 prefix-list Allow in
  neighbor 3.3.3.1 prefix-list Allow out
  neighbor 3.3.3.1 route-map Allow in
  neighbor 3.3.3.1 route-map Allow out
 exit-address-family
exit
!
ip prefix-list Allow seq 10 permit any
!
route-map Allow permit 10
exit
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