How to reduce time until routes are removed with BGP and Zebra?

[mlegner]

In my setup, I have a BGP session between a router and a host, and modify the host's routing table with Zebra. When a route goes down on the router, it takes ~30s until the route on the host is removed.

I would like to reduce this time to something on the order of 1-2 seconds. Is this possible?

My router's config (AFAIK the timers only affect the BGP session, not the exchanged routing information):

router bgp 65001
 bgp router-id 10.42.1.4
 no bgp ebgp-requires-policy
 no bgp default ipv4-unicast
 !
 neighbor 10.42.1.5 remote-as 65002
 neighbor 10.42.1.5 timers 10 30
 neighbor 10.42.1.5 advertisement-interval 1
 neighbor 10.42.1.5 timers connect 30
 neighbor 10.42.1.5 prefix-list NO_DEF_V4 in
 neighbor 10.42.1.5 route-map rm-out out
 !
 address-family ipv4 unicast
  neighbor 10.42.1.5 activate
  neighbor 10.42.1.5 soft-reconfiguration inbound
  redistribute kernel route-map allow-only-sgrp
 exit-address-family
!
ip prefix-list NO_DEF_V4 seq 5 permit 0.0.0.0/0 ge 1
!
route-map allow-only-sgrp permit 10
 match metric 15
!
route-map rm-out permit 10
  match metric 15
!

My host's config

router bgp 65002
 neighbor 10.42.1.4 remote-as 65001
 no bgp ebgp-requires-policy
!
interface ens5
!

[donaldsharp]

You can
a) lower your timers. You have a 30 second timeout
b) Use BFD for link detection and alerts when it goes down.

[mlegner]

Thanks a lot for the suggestions!

But does the hold timeout not only apply to the BGP session? I also want to cover the case where the BGP session is fine, but the router no longer has a route to a particular destination.

[ton31337]

This is for the same reason, keepalives + hold timer play here. Reduce them to something like 1 3 or so.

[mlegner]

Thank you both. I can confirm that using 1 3 as the timers reduces the route-eviction time correspondingly.