Solved: 2811 not dropping floating route, and going back to bgp-learned Primary route

mmertens · ‎03-06-2010

I have an ISR2811 with a primary BGP learned route via ethernet and a backup BRI connection with a floating static route (admin distance of 200). The site learns routes via BGP over the primary connection when the primary connection is in place. During a primary ckt failure, the BRI comes active and connectivity to the remote LAN works via the backup connection/floating static route. However, when the primary connection comes back, the router doesn't drop the floating static route/BRI and contintues to route over it.

If I remove the floating static route and re-add it; the router drops the BRI and routes over the primary link via BGP. I've tried an admin distance of 250 on the FSR. BGP come in with an admin distance of 20. Please see below.....Am I missing something simple? This is a new BGP config with a newly updated ISR (from 12.3 IP Base to 12.4 SP Services).

Thanks!

ROUTER#sho ip route 192.168.12.0
Routing entry for 192.168.12.0/24
Known via "static", distance 254, metric 0
Redistributing via bgp 65476
Advertised by bgp 65476
Routing Descriptor Blocks:
* 192.168.212.2
Route metric is 0, traffic share count is 1

ROUTER#config t
Enter configuration commands, one per line. End with CNTL/Z.
ROUTER(config)#no ip route 192.168.12.0 255.255.255.0 192.168.212.2 254
ROUTER(config)#do sho ip route 192.168.12.0
Routing entry for 192.168.12.0/24
Known via "bgp 65476", distance 20, metric 0
Tag 4323, type external
Last update from 198.18.23.145 00:00:05 ago
Routing Descriptor Blocks:
* 198.18.23.145, from 198.18.23.145, 00:00:05 ago
      Route metric is 0, traffic share count is 1
      AS Hops 2
      Route tag 4323

ROUTERconfig)#ip route 192.168.12.0 255.255.255.0 192.168.212.2 254
ROUTER(config)#do sho ip route 192.168.12.0
Routing entry for 192.168.12.0/24
Known via "bgp 65476", distance 20, metric 0
Tag 4323, type external
Last update from 198.18.23.145 00:00:15 ago
Routing Descriptor Blocks:
* 198.18.23.145, from 198.18.23.145, 00:00:15 ago
      Route metric is 0, traffic share count is 1
      AS Hops 2
      Route tag 4323

ROUTER(config)#do sho ip route 192.168.12.0
Routing entry for 192.168.12.0/24
Known via "bgp 65476", distance 20, metric 0
Tag 4323, type external
Last update from 198.18.23.145 00:00:17 ago
Routing Descriptor Blocks:
* 198.18.23.145, from 198.18.23.145, 00:00:17 ago
      Route metric is 0, traffic share count is 1
      AS Hops 2
      Route tag 4323

ROUTER(config)#end

Giuseppe Larosa · ‎03-06-2010

Hello Mmertens,

first show in first post is meaningful:

ROUTER#sho ip route 192.168.12.0
Routing entry for 192.168.12.0/24
Known via "static", distance 254, metric 0
Redistributing via bgp 65476
Advertised by bgp 65476
Routing Descriptor Blocks:
* 192.168.212.2

when primary route fails the secondary route is installed but it is also redistributed and advertised into BGP.

Being a locally generate BGP route it has a BGP weight of 32,768

when primary route comes back is not treated anymore as the best BGP path because BGP weight is looked first and makes the locally generated route to be preferred.

To have a correct behaviour in restore you can provide an higher weight to eBGP neighbors

router bgp 65476

address-family ipv4

neigh 198.18.23.145 weight 40000

this should solve your issue

Hope to help

Giuseppe

View solution in original post

KARUPPUCHAMY MALAIYANDI · ‎03-06-2010

Hi,

Can you paste the output of the below command

#sh run | b r b

I hope we need to refresh the BGP.

# clear ip bgp soft out.

Regards

Karuppu

mmertens · ‎03-06-2010

Karuppu,

Here's my BGP config: I can try try the the soft reset and see what happens. Thanks!

router bgp 65476
bgp log-neighbor-changes
neighbor 198.18.23.145 remote-as 4323
!
address-family ipv4
neighbor 198.18.23.145 activate
no auto-summary
no synchronization
network 172.30.1.0 mask 255.255.255.128
network 198.18.23.144 mask 255.255.255.252
exit-address-family
!

KARUPPUCHAMY MALAIYANDI · ‎03-06-2010

Hi,

Whenever the primary link comes up, obviously the BGP neighborship should be up.at that time can you check weather are you able to recieve the routes from your neighbor by the use of below command

#show ip bgp neighbors 198.18.23.145 received-routes

Can you check weather the necessary routes are present in your BGP table.

Can you paste the output the below command when static route is installed in your routing table

#sh ip bgp 198.168.12.0

Regards

Karuppu

Giuseppe Larosa · ‎03-06-2010