From: fwells12 (fwells12@xxxxxxxxxxx)
Date: Wed Nov 28 2001 - 04:28:23 GMT-3
Thanks for your reply Nigel. Unfortunately my topology is too complicated
to pass along.
In regards to you comments I want to point out that the router in question
has the loopback network in it's igp route-table prior to the network
statement being added to BGP on the router that has the loopback. Once that
is done, the other router loses it's igp route-table route. Now, that is
all well and good because it now learns the route via BGP which has a lower
AD -but the ip forwarding table does not get a replacement BGP route for
that network! The odd part for me is however that the BGP route IS injected
into the BGP table!!
'No sync' does remedy the problem but I want to understand why it is
behaving like it is...
----- Original Message -----
From: "Nigel Taylor" <nigel_taylor@hotmail.com>
To: <ccielab@groupstudy.com>; "fwells12" <fwells12@hotmail.com>
Sent: Tuesday, November 27, 2001 10:16 PM
Subject: Re: Has anyone come across this problem before?
> 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...
This archive was generated by hypermail 2.1.4 : Fri Jun 21 2002 - 06:45:24 GMT-3