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New Member

Why 'show ip bgp' shows nothing ?

On RouterB, I do 'show ip bgp' and no info is displayed. I expected that after issuing 'show i bgp', I would see Network '1.0.0.0' advertised. Can someone clarify what am I missing ? PLease find output from 'show run' and 'show ip bgp neigh' as an attachment.

C2610 RouterA is on AS 100, s0/0=192.1.1.1/24 (DCE)

Loopback0=1.1.1.1/24

Connected via V.35 serial cable to

RouterB, AS 200,

s0/0=192.1.1.2/24

Loopback:2.2.2.2/24

8 REPLIES
New Member

Re: Why 'show ip bgp' shows nothing ?

Hello,

Router B will not see this route as a BGP route because it is directly connected and because Router B is the source of the route.

To confirm that Router B is advertising the route you want to issue "show ip bgp neighbors x.x.x.x advertised-routes" from Router B.

If the route is being advertised then it should show up under "show ip bgp" on Router A.

HTH.

-Rob

Hall of Fame Super Bronze

Re: Why 'show ip bgp' shows nothing ?

Marlon,

On Router A, you need to issue the following

network command.

network 1.1.1.0

instead of

network 1.0.0.0

Also, I recommend disabling synchronization on routerB since I see you are doing iBGP there.

With synchronization enabled, routes learned via iBGP peers won't be installed in the routing table. They have to be learned via IGP.

Please rate helpful posts.

Thanks

Silver

Re: Why 'show ip bgp' shows nothing ?

In additional to Edison's post. You can simply add "redist connected" under BGP in router A. Then you can find the route of 1.1.1.0/24 and the LB address in BGP table.

Hope this helps.

New Member

Re: Why 'show ip bgp' shows nothing ?

In reality, the network is 1.0.0.0, therefore I did

router bgp 100

network 1.0.0.0

redist connected

and that did it.

I certainly read what the 'redistribute connected' command means but I am not sure if I understand correctly; is this supposed to advertise all routes to external AS ?

RouterB#show ip bgp

BGP table version is 14, local router ID is 2.2.2.2

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale

Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path

*> 1.1.1.0/24 192.1.1.1 0 0 100 ?

r> 192.1.1.0 192.1.1.1 0 0 100 ?

Re: Why 'show ip bgp' shows nothing ?

Hi,

You don't need to configure both - 'network' & 'redistribute connected'. These are two different options to advertise routes via BGP.

The only reason why the route wasn't being advertised earlier with the network command is because your subnet mask for network 1.1.1.0/24 was incorrect. You were using a /8 bit mask instead of /24 bit mask. BGP wouldn't advertise a route if the mask used with the 'network' command isn't consistent with the actual route itself.

The 'redistributed connected' would redistributed all connected interfaces (networks). You can configure 'redistribute connected' with a route-map and specify which networks need to be redistributed.

Hence, you can safely remove the redistribute connected command and configure the 'network' command with the /24 bit mask. After any config change issue the command clear ip bgp soft * for the config change to take effect.

router bgp 100

network 1.1.1.0 mask 255.255.255.0

no redistribute connected

If you prefer you can use the redistribute connected command and in that case you don't need the 'network' statement under the BGP process.

Hope that helps!

Sundar

New Member

Re: Why 'show ip bgp' shows nothing ?

True. I did 'no redist connected' and specified network 1.1.1.0 mask 255.255.255.0 and it works fine.

Thanks all for your help. You are rocking.

Silver

Re: Why 'show ip bgp' shows nothing ?

Yes, it will advertise all Connected / local interface to the BGP. I suggest it because of the simple config or you don't want to use mask for the subnet.

So if you only want to advertise 1.1.1.0/24 then you can use network 1.1.1.0 255.255.255.0 command. If you want to advertise all local active interface, then you can use redistribute connected to simplify the config. If you only want to advertise the network of such interface but not want to enable BGP for that interface, you can use passive-interface command to prevent that interface to enable BGP and advertise route from it.

Hope this clarify.

Cisco Employee

Re: Why 'show ip bgp' shows nothing ?

You would actually need to configure network 1.1.1.0 mask 255.255.255.0. Without the configuration of an explicit mask, the default mask of 255.0.0.0 would be used.

Hope this helps,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México 
Paseo de la Reforma 222 Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
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