Cisco 3550 brings 3COM network down

[augman]

I currently have some 3com superstack switches. When I try to connect a Cisco 3550 EMI switch, the network goes down. Any ideas as to what I need to configure?

 

[TimRegester]

When you say it goes down what do you mean?

I would suspect it is a spanning Tree issue with the 3550 possibly becoming the root bridge and screwing the Spanning Tree up on the 3Com network. look for topology changes on 3Com switches attached to the 3550.

 

[skhalil]

Hi augman,

I am having exactly thesame problem that you had. Please let me know what are your findings on this issue. Whenever I plug in 3548 (EMI) in to network with 3 COM and couple of other cisco switches it brings down a portion of network.

thanks

 

[ADB100]

This looks like your network may already be broken. By default the 3Com kit WON'T have Spanning-Tree enabled, the Cisco kit WILL. If you connect the Cisco switch and it detects an STP loop it will begin to block on whatever ports it sees as the Layer-2 'Worst' link (based on the STP root, port priorities etc).
I would draw a nice picture of your current network topology (including VLANs) and then work out if you have any loops and then try and engineer the Cisco switches into this network. Either that or pay for someone to come and sort it out for you.

I happily use 3Com & Cisco switches (and routers) together and as long as you know the limitations between them its not difficult.

Andy

 

[skhalil]

Thanks Andy, beside looking at some of the other issues I was already working on the spanning tree issue and was trying to find the loops. Your suggestion has made me more convinced on spanning tree issue.Thnka once again.

Sohail