From: Nigel Taylor (nigel_taylor@xxxxxxxxxxx)
Date: Wed Nov 28 2001 - 03:16:44 GMT-3
fwells12,
I'm a bit lost as to the layout of your sample topology?
Remember that if the route is being advertised through the IGP(eigrp, ospf,
etc..) then let's say you advertise that route into bgp(using the network
command) then it would depend on how the router in question is
learning/receiving the BGP routes for the network(loopback) in question.
If the router is receiving a eBGP route then what you see is correct in that
eBGP AD is 20, which would be better that the IGP metric from EIGRP or OSPF.
This eBGP route would replace the existing route.
Also, that eBGP route using most-likely the directly connected interface
would then have a valid route to that network and in effect add the route to
both the BGP table and the RIB.
>BGP is not supposed to enter a route into the BGP table unless it has a
route
> in it's IGP table first right?
This is correct.
The important thing to remember here is there are inbound and outbound rules
that apply here as it pertains to eBGP routes versus iBGP routes, entering
an ext AS's or moving within an existing AS.
But remember once you disable "synchronization" you are allowing bgp to add
a route(s) from the BGP table to the RIB, by telling BGP to overlook the
requirement of having a route/path in the RIB.
Post the config and route table in question..
- Nigel
----- Original Message -----
From: "fwells12" <fwells12@hotmail.com>
To: <ccielab@groupstudy.com>
Sent: Wednesday, November 28, 2001 12:02 AM
Subject: Has anyone come across this problem before?
> I have a route in my igp that disappears when I advertise that route from
BGP.
> The network is on a loopback interface being redistributed from EIGRP to
OSPF.
> Before I add it to BGP, all my other routers (regardless of IGP) can see
it
> just fine. Once I add it to BGP via a network statement all my BGP
speakers
> can see the route in their BGP tables (including the router in question)
and
> in all their IP forwarding tables as BGP routes -except the router in
> question. The odd thing is, the router that does not have it in its IP
> forwarding table any more, does have it in its BGP table! -how does that
work?
> BGP is not supposed to enter a route into the BGP table unless it has a
route
> in it's IGP table first right?
>
> Sync is enabled
> IOS is 11.3 IP/IPX/AT/DEC and has been used extensively without previous
> problems.
>
> Thoughts please...
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