Expert Advice needed - mind bender

[jramsey]

Ok, so this is not so much a Cisco question as much as it is a..."What the heck is going on here" sorta question. I have a feeling that this might be a stumper, but hopefully someone out there has an answer. So here is the problem...

We are currently running both a Token-ring(I know, I know, but we are migrating, trust me ;p ) and ethernet network. There is an old baynetworks router connecting the ethernet and token-ring segments both then go out a Cisco router to the internet. The router between the two segments is wide open, no ports closed etc, etc, it is strictly there to convert TR packets to ethernet.

We are accessing a website fine on both segments, however there is one part of this website that we can only access on the Ethernet side. This piece of the site is using port 9151 to access it and uses a client on the local machine to connect to this portion of the site. 8 months ago there was no problem going over the token-ring to access this site. And to the knowledge of the staff, nothing has changed on this end.

It is possible I am overlooking the obvious, but so far nothing rings a bell. Any ideas would be welcome and many thanks go out to those who can help!

- Justin Ramsey

CCNP/MCSA/MCSE

[thisisshanky]

What about communication in and out, from that client on the token ring side, to other websites....

Also can u check to see if you get a packet sourced from that client in the token ring subnet, outbound, reaches the router (cisco).

This can be done by using a debug command. Try giving this during off peak hours.

debug ip packet 101

where 101 is an access-list defined , as follows

acces-list 101 permit ip host any

If you are using udp or tcp ports, you can filter the debug output more, using tcp /udp keyword instead of ip on the ACL and also use, "eq 9151" at the end of the access-list after the "any" keyword.

[jramsey]

Well, I actually came accross something that worked. I don't know how, but changed the MTU to 1500 (enet) and it worked

[jramsey]

btw, thanks all for the help to all who gave this a thought!

[warren]

What this sounds like is an MTU mismatch. Can you try setting the MTU on the machines on the token-ring segment to be the same (or smaller) than that on the ethernet segment? Also, is there any multi-cast happening? Multi-cast and token-ring is sometimes odd!...

[jramsey]

That actually was it, I wish I would have asked this question long ago, I could have used your help! I really appreciate the reply, found the issue literally just minutes before the reply, but you certainly didn't take long to figure it out! Thanks so much for the help, it is very much appreciated. I was racking my brain on this for days.

[warren]

No worries!