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Unbale to get proper BGP route on remote locations for Fastethernet interface with Primary and Secondary IP address

Hi All,

Below is the configuration done on one of the routers. But remote end sites are not getting route at remote lactions via BGP.

IP address @ FastEthernet0/0

  • Prim IP:-
  • Sec IP :-

Static Route
ip route

Network advertised in BGP


interface FastEthernet0/0
ip address secondary
ip address
ip access-group 110 in
no ip redirects
no ip unreachables
no ip proxy-arp
ip flow ingress
ip pim sparse-mode
ip route-cache flow
no ip mroute-cache
speed 100

router1#sho running-config | begin bgp
router bgp xxx
-output omited-
network mask
neighbor X.X.X.X remote-as xxx
-output omited-

Tried removing secondary IP from LAN interface and was geting proper route at other end for primary address with same /22 advertisement.

Also added secondary IP address again and advertised specific subnets(network mask, network mask ) from BGP at source routes were properly learnt.

router1#sho running-config | begin bgp
router bgp xxx
-output omited-
network mask

network mask
neighbor X.X.X.X remote-as xxx
-output omited-

Can anybody help me out in finding root cause for this?

5 Replies 5

Forgot to mention IOS on router.

sho version
Cisco IOS Software, 1841 Software (C1841-SPSERVICESK9-M), Version 12.4(12a), RELEASE SOFTWARE (fc3)
Technical Support:
Copyright (c) 1986-2007 by Cisco Systems, Inc.
Compiled Thu 22-Feb-07 15:56 by prod_rel_team

ROM: System Bootstrap, Version 12.4(13r)T, RELEASE SOFTWARE (fc1)

Router1 uptime is 1 day, 10 hours, 30 minutes
System returned to ROM by power-on
System restarted at 22:54:27 GMT Mon Jan 11 2010
System image file is "flash:c1841-spservicesk9-mz.124-12a.bin"


Hi Manoj,

What do you want to achieve exactly?

You can insert routes into BGP in several ways (network, redistribuiton) but the main thing is that prefix(es) has to be in the routing table already otherwise BGP will not advertise.

Another important thing is the prefix to be advertised has to exactly match the one in the routing table. I'm not talking about here the summary.

The easiest way to do it with network statement and create a static route to null to have the prefix installed in the routing table.

router bgp

network mask

ip route null0

Hope it helps, rate if does


Hi Krisztian,

Thanks for the responce.

The issue here is when i am configuring secondary IP on lan interface, the network is not getting advertised to BGP neighbours.

Can somebody suggest why?


If I understand correctly once you added the secondary prefix under the network command it was working fine.

It is becasue as I wrote the network command has to exactly match the prefix already in the routing table.

If you want to have both prefixes advertised (i.e not a single one covering both) then you need to have the two network statement. In case you need a single entry covering both let's cover them with and create a static route for the same pointing to null.

Hope this helps, rate if does


Thanks a lot again...

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