From: paul cosgrove (paul.cosgrove@gmail.com)
Date: Wed Jan 28 2009 - 17:56:15 ARST
If I understand you correctly then two routers are peering with the same
neighbor, and both are using the same IP address in their neighbor commands
to identify this common neighbor. Only one BGP session remains up at any
one time.
Just a guess based on what you have said so far, but if you are using eBGP a
possibility* is that either:
- one of these two spokes is advertising the route used by the common
neighbor to get to the other spoke, or
- one of these two spokes is advertising the route used by the other spoke
to get to the common neighbor.
This is obviously more likely if you are peering between IPs which are not
directly connected, but if you are advertising a route which is more
specific than a directly connected interface of the receiving router then
would still occur.
If this is the scenario then you could increase the number of hops allowed
by ebgp multihop (or use that instead of disable-connected-check).
Paul.
*Note: This wild guess comes with no guarantee, and may have only a slim
chance of being right. Readers should be aware that accuracy can go up or
down based on supplied information.
On Wed, Jan 28, 2009 at 3:10 PM, Piotr <usaccie@gmail.com> wrote:
> Post your config. I never heard of two peers using one IP.
>
>
>
> On Mon, Jan 26, 2009 at 2:30 PM, Vladimir Sousa <vladrac@gmail.com> wrote:
>
> > Hello there,
> >
> > Anyone has seen a problem where you cannot establish 2 BGP sessions over
> a
> > single IP?
> >
> > I have 2 switches trying to use a single IP in another switch as a BGP
> peer
> > and only one is successful.
> >
> > If I shut one neighbor down , the other goes up.
> >
> > neighbor ip shutdown
> >
> > Makes no sense to me and looks like a BUG or something.
> >
> > Any ideas?
> >
> > Regards,
> > Vlad
> >
> >
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