our network consist of 2 switches 6513 SUP720 12.2(18) in distribution layer and a number of bladeservers with cisco switches. CIGESM 12.1(22)EA9.
every blade switch is connected to one 6513 with one etherchannel port (2 interfaces), one usual interface(dedicated for NFS) and additional one usuall interface (oracle cluster interconnection).
We're running MST spanning tree...
config is here:
Instance Vlans mapped
6513 is root for all MST instances
Today a cable was reconnected to the interface on bladeswitch, that was not correctly configured with Oracle VLAN and after that ALL bladeswitches put their etherchannel connection and Oracle connection in err-disable mode: "loopback detected"
First important question:
Is it correct that I move all VLAN's, including VLAN1 from MST0? all switchblades are connected as "Pre-STD"
the MST config of blade switches is in attach.
If a bridge learns a mac address M on a port P (by receiving a frame with M as a source mac address), it means that in the current topology, the device associated with M is off port P. As a result, if the bridge later receives a frame with M as a destination address on port P, it's going to discard it because it knows that the frame will reach its destination without the need to be switched through the bridge.
The loopback message plays a little trick with the learning function of the bridge as its source mac address is the same as its destination mac address. If the cam table does not contain the mac address of the loopback message, it is flooded. After that, it's going to be filtered. So the chance of a loopback message traveling across the network is really when there has just been a topology change that has flushed the cam tables. (and BTW, connecting a cable generally leads to a TC, when the port goes forwarding).