Thank you Dominik for the info.
Current STP Operation Mode: STPG is running on Nortel Baystack 470-48T and RSTP is running on C6500.
Actually what is happening is randomly some of the desktops are going out of network for 1 mins and reconnects on its own. The issue is sporadic in nature. Upon checking at Cisco 6500 i see TCN changes counter is very high coming from interface where nortel 470-48T is connected. Also i see some of the edge ports in Nortel switch rate-limit counters is showing 99% traffic for multicast and Broadcast.
So i assume it could be the issue with any sorts of loop. But i am new to nortel environment and dont have much idea to see the TCN changes in Nortel.
Also, i m not sure if it is because of loop, can anyone help to understand the such issue?
Really appreciate your help. Thank you.