We have a LAN of 20 switches - 19 L2 2950 and one L3 3560 switch. Total number of VLAN are 20. L3 swicth acts as the default gateway of all VLAN - subnet. All the servers are attached to L3 swicth. Default STP is running on all switches and one of the L2 switch has been chosen ( automatically ) as root bridge. Now as we added VLAN ports to the swicth directly connected to L3 swicth( server switch ) suddenly server access became very very slow from all over the network. so we rolled back the switch configuration to original that is all ports in the VLAN1 ( that is also the server VLAN ) except trunk ports. CPU utilization was only 8 %. Then I added back the ports to VLAN one by one and not by using interface range command. After adding each port to VLAN I checked the server access, it was perfect. So after 40 iterations all the necessary ports were in the new VLAN and also server access was perfect. I didnt get exactly the reason why server access became suddenly slow and again back to normal after adding the ports step by step. As a safe precaution we have rolled back the switch configuration to original. What I feel is that recalculation of STP for that time has slowed down the server access. Coincidebtly server swicth has only one trunk ( that is bad design - single pt of failure !! ). In full network there is only one redundant link. What can be the possible reason for sudden slow responce of the network. In default STP version do switches run STP for each VLAN that means we are running 20 STP instances and that might have caused the sudden delay in the network access.
Please share the experience.
Any link on cisco.com is highly appreciated.
Thanks in advance.