From: miken (miken@sisna.com)
Date: Wed Feb 12 2003 - 16:05:49 GMT-3
I suspect you have not disabled synchronization in router bgp on routers 1
and 2. The are iBGP peers and by default, will not advertise routes to each
other that are not synchronized with an IGP....in other words aready in the
routing table. You probably can see the routes in "show ip bgp", but not in
the routing table. Disable sync and that should solve your problem. URL and
quotes from Cisco:
http://www.cisco.com/warp/customer/459/bgp-toc.html#synch
"Synchronization states: If your autonomous system is passing traffic from
another AS to a third AS, BGP should not advertise a route before all
routers in your AS have learned about the route via IGP. BGP will wait until
IGP has propagated the route within the AS and then will advertise it to
external peers. This is called synchronization. "
Thanks,
Mike
----- Original Message -----
From: "Richard Young" <cc_young@pacbell.net>
To: <ccielab@groupstudy.com>
Sent: Wednesday, February 12, 2003 11:26 AM
Subject: BGP Multihoming Two IBGP Routers to Two ISPs
> Hi,
> I have a question about a lab I am working on. The Lab has 5 routers.
> R1 and R2 are directly connected ibgp neighbors in AS1001.
> R3 is connected as an EBGP neighbor to R1 in AS 300.
> R4 is an EBGP neighbor to R2 in AS400.
> R5 is an EBGP neighbor ro both R3 and R4 in AS 500
>
> R5 has one loopback 200.100.1.1 /24
> R5 has one ethernet 200.100.2.0 /24
>
> After all neighbors are established, I see two bgp paths to both networks
> of R5 on R1, but I only see one path to both networks of R5 on R2.
> It is like R1 is getting both networks but not forwarding them to R2.
>
> My goal is to use BGP communities to set local preference but without
> seeing both paths on both routers with the command "show ip bgp" the
> route maps so not see the bgp paths and do not work.
>
> Is there some BGP rule similar to split horizon that prevents IBGP
> neighbors from sending all routes to all other fully meshed IBGP neighbors
> in the same AS?
>
> Thanks in advance.
> Richard
> .
.
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