From: perkinsr@xxxxxxxxxxxxxx
Date: Wed Jul 10 2002 - 12:51:28 GMT-3
Thanks for the help, since my last note I have made the following 2 changes:
Eliminated the 2924 by using a cross over between R7 and R5
Changed IP MTU on the TR to 1500
I can get adjacency when I use non-broadcast netowork type and a Neighbor
statement on each router. This is when I remembered the MTU mismatch, I was
getting DBD problems while trying to form an adjacency.
Using Broadcast network types and Debug IP packet I see the R2 sending
multicasts out the TR interface, R5 sees these and replies with a multicast
but those packets aren't making it back to R2. The bridge R7 would appear
to be dropping those packets for some reason. I don't know why and I don't
know what debug commands to use to troubleshoot the bridging process.
Eigrp seems to show the same symptoms, this looks like an issue with
translating multicasts from ether to TR, the 7500 seems to just drop
multicasts when going from ether to TR.
If I ping the boadcast address 137.20.20.255 I get the appropriate reply on
both R2 and R5.
I am bridging between two other routers that are both TR through the same
7500 and they work fine with both OSPF and EIGRP.
-----Original Message-----
From: Oliver Boehmer [mailto:oboehmer@cisco.com]
Sent: Wednesday, July 10, 2002 8:02 AM
To: perkinsr@WellsFargo.COM
Cc: ccielab@groupstudy.com
Subject: Re: OSPF adjacency over Token to Ether bridge
Hi,
never tried this myself, but you have two issues in this environment:
- Multicast address issue
- MTU difference
OSPF will not form an adjacency if MTU is different. You can turn off the
check with the interface command "ip ospf mtu-ignore", or you can lower the
"ip mtu" on the TR.. I think the latter is better, because even if you
disable the MTU check, large DBD packets sent from the TR side can't be
handled by the ethernet..
I heard that this setup works when using "ip ospf network non-broadcast"
and statically define the neighbors.. Should be an acceptable solution..
How far do you make it in the OSPF neighbor state? You might want to check
http://www.cisco.com/warp/public/104/12.html
oli
At 07:25 10.07.2002 -0700, perkinsr@WellsFargo.COM wrote:
>I am working on lab 5 in my make-shift lab. Most of my routers have token
>ring, but a few are ethernet, to overcome this obsticle I have all the
token
>interfaces connected to a 7500 (R7) and all the ethernet interfaces
>connected to a 2924 (SW0). The 7500 also has connections to the 2924. In
>order to get the topology I need I am using the 7500 to bridge between
token
>and ethernet. I have that much working, I can ping from the ethernet to
the
>token interface, but I can't get OSPF to come adjacent. I suspect there is
>an issue with translating multicast traffic from token to ether. Does
>anyone know what might be the problem?
>
>
>
>R2-----O-----R7-------SW0-------R5
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