Question : Voip Issue 3com Baseline Switch 2924

Hi!
I have a strange issue with 2 IP Phones (AASTRA Office 70 IP -b).
My network has several 'old' AASTRA 35 IP Phones and only 2 '70 IP Phones'.

I recently updated old unmanaged switch with newer 3Com Baseline Switch 2924 (managed) and all is working fine EXCEPT for the new 2 IP Phones. They cannot connect to PBX. If I use an old switch, all is working fine.

The other strange thing: If I use the older switch, the IP Phones are able to connect to PBX. If I, once connected, change the Network cable to newer 3Com Switch, the continue to work! (obviously, with a momentary loss of network connectivity).

So, the problem seems to the very initial connection to PBX.

Any clues?

Thanks.

Answer : Voip Issue 3com Baseline Switch 2924

Spanning Tree Protocol Issue. Disabled it on Switch and the IP phones are working.

It's time to investigate on.......