Inter-mixing Nortel and Cisco

[said07]

I have an existing Nortel 450 backbone and decided to add to it 2 cisco CE500 /24p to no avail.
The Nortels are connected to each other with a trunk (etherchannel).
I placed a cisco on each Nortel.

!-----------------------!
Nortel Nortel
! !
Cisco Cisco

The ciscos were configured with static ips and as follow: ports 1-4 for access points, 5-20 for desktops, 21-24 for switches.

The first time I connected the ciscos to the nortels through the g1 port it created a storm and brought down my entire network.
The second time, I connected them through port 24, that didn't create a storm but i had no connectivity.

Any suggestions please?

Thanks,

Said

 

[BuckWeet]

As you are using multiple ports for the uplink, how do you have it setup? port channel?? also do you have spanning-tree enabled?

 

[jneiberger]

If a storm brought down your network then you probably created a switching loop somehow. I would ask the same things that BuckWeet already asked. If you have a loop-free topology this won't happen. If you can't be physically loop-free then properly configured spanning tree is a must.

 

[said07]

Yes, spanning tree is enabled on the Nortels. I guess it is also on the Ciscos by default.
For the uplink, I used for the first time G1 and that's where I had the storm. The second time I connected the ciscos to the nortels through port 24 which was configured by the wizard for switches connectivity.
I didn't use multiple ports. Just one.
As you see from the drawing there was no loop.
The amazing thing is that I did the same thing at home and everything worked just fine.
I connected 3 ciscos to a nortel in a stand alone config (a wire to each from the nortel). I even stacked them all three and connected only one to the nortel and everything was just peachy.
Is spanning tree enabled by default on cisco and what do you mean by "then properly configured spanning tree is a must." How do you do that?
Thanks for your time guys.

 

[yawnbob]

I had a similar setup with a Cisco 3560 behind a Bay 450 and it would bring down the whole network (98% Nortel). I eventually disabled STP on the 450 uplink port, never did find out exactly what the problem was. If you use the Cisco wizard it defaults many "safety" features into the config like "spanning-tree loopguard" and "switchport port-security". I had another issue with the port-security command shutting down the switch because it detected the Nortel switch it was uplinked to. I know this isn't an answer to your problem but I would stress that using the wizard may cause more headaches than you know.