You would want to use Rapid Per VLAN STP and the core switch as your root bridge: In 6509: % Enable Per VLAN STP %spanning-tree mode rapid-pvst % Make sure a different Bridge ID is used for each VLAN %spanning-tree extend system-id % Force the core s...

Have you configured the default gateway on each PC ?

This sounds like a layer 2 loop, however, you would need to provide details for anyone on this forum to be able to identity the issue.

5 is the severity level which means everything between 0 and 5 is logged. The facility value is used to calculate the priority value of the message which is done by below formula: Priority value = (facility value*  + severity value These are the fac...