I'll elaborate a bit more. My fault.
The BGP route in question is actually being learnt by OSPF and is in the route table.
On BGP peers which have an EBGP session, that route is in the BGP prefix table, but
comes in as "not sync..." when doing a sh ip bgp x.x.x.x
Now, when I put it a static route on with a lower administrative distance, which
therefore overwrites the OSPF learnt route, with the same info (next hop. etc), the
BGP route becomes synchronized immediately, like magic :). When I change the IGP to
RIP, it also works. (Boy have I spent some time on this one). Revert back to OSPF
and no good. Again.
Maybe it's a version thing, but with the exam coming up, I don't have the inclination
to upgrade all my routers to something else. I'm running 11.2 GD.
I know inserting no synchronization works, but I'd like to know why I need it with
OSPF, but not with RIP and statics.
Halabi's book, whilst a pretty good read, seems to stick no sync in every example they
have, even when the example would show that it is unnecessary.
Thanks
Scott
-----Original Message-----
From: Nigel Taylor [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, 26 September 2000 1:23 PM
To: Scott Aitken; [EMAIL PROTECTED]
Subject: Re: bgp and ospf and synchronisation
It seems to me that you've answered your own question. I currently run OSPF
<--> BGP without the command 'no sync" on my EBGP peers. I've you carefully
read the rfc, or any BGP related document you'll discover that two
requirements must be meet in order for BGP to fully synchronized. The 2
requirements being that BGP knows of the route through redistribution or the
use of the network command. An secondly, the network being advertised must
be present in the route table(RIB). This would explain the ability to make
static routes and have BGP synchronized. I'm sure if you check your
running OSPF(IGP) routing tables for the networks that aren't synchronized
with BGP you will not find a route to these networks in your routing table
at all.
HTH
Nigel.
----- Original Message -----
From: Scott Aitken <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Tuesday, September 26, 2000 3:29 AM
Subject: bgp and ospf and synchronisation
> Does anyone know of a problem running OSPF as your IGP with BGP?
> BGP seems to have trouble checking the routing table entries (for the
purposes of IGP synchronisation) when then are inserted by OSPF. With OSPF,
it seems you need to stick "no synchronization" on all the BGP peers running
EBGP.
> I have a test network with OSPF and BGP. When I replace OSPF with RIP, or
even statics, the BGP routes are immediately synchronised, but with OSPF
they never are; hence the need to run "no sync...".
> Any thoughts?
> Regards
> Scott Aitken
>
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