Mailing List Archive: [nsp] OSPF

[nsp] OSPF

Oct 10, 2002, 3:54 AM

Post #1 of 3 (1117 views)

Hi,

I am making some experiments and I have a problem when OSPF is running.

This is the net topology where R3 is never running any routing protocol.

Router1----Router2----Router3

R1 has a loopback IP address pingable from R2 and R3.

I set up an loopback interface on R2 whith the same IP address as R1, but I keep the loopback interface of R2 shuted down.

Now if OSPF is not running between R1 and R2, R3 can ping R1 loopback interface.

But if OSPF is running between R1 and R2, then R3 cannot ping R1 loopback interface. (although I set it up as passive-interface.) Why?

If someone has an idea to share with me, he is more than welcome.

Thank you.

Regards,

Christophe

------------------------------------------

Faites un voeu et puis Voila ! www.voila.fr

Re: [nsp] OSPF [ In reply to ]

msa at samurai

Oct 10, 2002, 6:29 AM

Post #2 of 3 (1084 views)

Permalink

On Thu, Oct 10, 2002 at 12:54:30PM +0200, odusseus wrote:
> I set up an loopback interface on R2 whith the same IP address as R1, but
> I keep the loopback interface of R2 shuted down.
>
> Now if OSPF is not running between R1 and R2, R3 can ping R1 loopback
> interface.
>
> But if OSPF is running between R1 and R2, then R3 cannot ping R1 loopback
> interface. (although I set it up as passive-interface.) Why?

I suspect you'll find that both boxes have the same OSPF router ID.
End result, R2 drops all information from R1, and doesn't forward traffic
to R1 for that loopback address. The traffic terminates locally, where the
interface is shut down, and thusly there is no response.

Or something along these lines -- I'm pre caffeine. Configure a
different loopback address on R2 and it should work fine.

--msa

Re: [nsp] OSPF [ In reply to ]

hritter at cisco

Oct 10, 2002, 6:42 AM

Post #3 of 3 (1083 views)

Permalink

Christophe,

Could you include a "sh ip ospf da ro".

Thanks,

At 12:54 PM 10/10/2002 +0200, odusseus wrote:
>Hi,
>
>I am making some experiments and I have a problem when OSPF is running.
>
>This is the net topology where R3 is never running any routing protocol.
>
>Router1----Router2----Router3
>
>R1 has a loopback IP address pingable from R2 and R3.
>
>I set up an loopback interface on R2 whith the same IP address as R1, but
>I keep the loopback interface of R2 shuted down.
>
>Now if OSPF is not running between R1 and R2, R3 can ping R1 loopback
>interface.
>
>But if OSPF is running between R1 and R2, then R3 cannot ping R1 loopback
>interface. (although I set it up as passive-interface.) Why?
>
>If someone has an idea to share with me, he is more than welcome.
>
>Thank you.
>
>Regards,
>
>Christophe
>
>------------------------------------------
>
>Faites un voeu et puis Voila ! www.voila.fr
>
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Harold Ritter, CCIE 4168
Advanced Network Services - ISP East
Cisco Systems
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Chelmsford, MA 01824 USA
Phone: 978 497 3129
Fax: 978 497 3129
Cisco Systems- "Empowering the Internet Generation."