Nortel to Cisco Wan Link

Posted on 2003-02-27
Medium Priority
Last Modified: 2008-03-17
I have a nortel Router in one site runing LLC, IP and ospf. I need to put a cisco at the other end of the Wan link. I have verfied that the T1 is good by having 2 Cisco's at each end and 2 nortel routers on the ckt. when i mix the rotuers i have can not get the circuirt up and running. I have configured both ends with IP and the proper subnet.
enc PPP

I am not sure where to go from here.
Question by:JaysonJackson
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LVL 79

Expert Comment

ID: 8033459
If you are using ppp encapsulation, on the Cisco side, try setting the serial interface mtu to 1492 to match the Nortel

Author Comment

ID: 8033516
Tried setting the MTU to 1492 no line still down. I belive the LLC layer is not comming up and i am not sure why.
LVL 50

Expert Comment

by:Don Johnston
ID: 8034021
It's been awhile since I worked with a Nortel router (actually, they were called Bay routers back then :-)). but I recall them having two serial encapsulations Standard (which was Bay's HDLC) and PPP. When we connected a Bay to a Cisco using serial links, we set the interfaces to PPP on both ends.

When Nortel acquired Bay, did they change the terminology and now they're refering to PPP as LLC?

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LVL 79

Accepted Solution

lrmoore earned 2000 total points
ID: 8034646
Found this on a nortel FAQ site. I had the MTU adjustment at the wrong end. Agree w/Don that you need a common encapsulation at both ends
How do I get a Bay to talk to a Cisco on a Pt-Pt line?
last updated: 5/18/1999

A. Both Cisco & Bay default to a proprietary HDLC on WAN circuits. So, they won't talk to each other by default.

However, you can use PPP, which is an RFC standard WAN protocol, and get them to communicate.

Hang on a minute, first. You also have to change the default MTU sizes.

Bay defaults to 1600 bytes and Cisco defaults to 1500. Also, Bay doesn't include the datalink header in its MTU count. So, you should set the Bay's MTU to 1506 and leave the Cisco to it's default.

Test it by sending a 2000-byte ping through. If it works, then the MTU size is fragmentting correctly.

If you need clocking, then let the Cisco provide it.


Author Comment

ID: 8066483
This work with a little more research but this pointed me in the correct direction.
LVL 79

Expert Comment

ID: 8066508
What was your final thing that made it work?

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