BGP routes not appearing

[bobtfmac]

Setting up 2 BGP peers in same AS in a lab. As I understand BGP you don't need explicit network statements in BGP for directly connected peers to advertise routes to each other yet the directly connected ethernet ports' subnets won't show up in the connected routers bgp table unless I put them in.

 

[mainstreetexpress]

Are the Ethernet interfaces up/up?

 

[baddos]

Unless I'm reading your config wrong both your routers are using the same IP addresses for their interfaces.

Can you post a "show ip bgp summary" as well?

 

[bobtfmac]

My bad, copied the same router config twice. Attached is new corrected file along with:

<b>sh ip bgp summary</b>
and
<b>sh ip int brief </b>

AND the results of removing the network statements on Tuscon (routes disappear from Dallas' bpg table)

For grins, did not remove network statement on Dallas for it's ethernet and Tuscon continues to show a bgp candidate route for Dallas:

Tuscon#sh ip route
.
removed for clarity
.
.
Gateway of last resort is not set

10.0.0.0/24 is subnetted, 4 subnets
B 10.2.8.0 [200/0] via 10.2.5.2, 1d00h
C 10.2.2.0 is directly connected, Ethernet0/1
C 10.2.5.0 is directly connected, Serial0/0
C 10.2.6.0 is directly connected, Ethernet0/0
Tuscon#


One idea -> there may be no actual hosts on the ethernets, maybe this is the cause?

 

[jneiberger]

BGP does not advertise any networks you don't tell it to advertise. Unless you're redistributing connected routes into BGP or using explicit network statements, your connected routes will not be advertised.

 

[baddos]

You do need the network statements if you don't redistribute. A BGP router should never automatically send routes out as this could lead to a very dangerous Internet. hehe

Here is a quote from Cisco's site talking about the network command:

The network command is used to inject IGP routes into the BGP table. The network-mask portion of the command allows supernetting and subnetting. The router's resources, such as configured NVRAM or RAM, determine the number of network commands you can use. Alternatively, you could use the redistribute command to achieve the same result.

A problem that I see is that the "Dallas" router isn't receiving any prefixes from it's peer.

Dallas#sh ip bgp summ
BGP router identifier 10.2.8.2, local AS number 2
BGP table version is 13, main routing table version 13
1 network entries using 101 bytes of memory
1 path entries using 48 bytes of memory
1 BGP path attribute entries using 60 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 209 total bytes of memory
BGP activity 6/5 prefixes, 6/5 paths, scan interval 60 secs

Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
10.2.5.1        4     2    1569    1564       13    0    0 1d01h           0

It's not learning the 10.2.2.0/24 and 10.2.6.0/24 because you removed them from Tuscan's bgp config. Since you have no default route on Dallas, you will need to learn those routes by a routing protocol or manual static routes.

 

[bobtfmac]

Thanks. The confusion I have is due to the examples in the BGP book which show peers learning each others' routes without any network statements. I'll look closer, maybe there is redistribution going on which I missed.

 

[jneiberger]

BGP does not automatically advertise any routes. You have to tell it what you want to advertise.