MSTP doesn't work with multiple instance

[adiltaleb]

Hi,

i have a problem with mstp managing 2 instance plus 0.

i have configured instance 1 to support vlan 1 12 and instance 2 to support vlan 10.



I have configured two 7750, the first is root primary for instance 0 and 1 and root secondary for instance 2.

the seconde is root secondary for 1 and root primary for instance 2.



on stack 4500, i have configured the 2 instance: 1 for VLAN 1, 12 and 2 for vlan 10 and i have configured to trunk port connected to the each 7750.



G1/0/26 connected to first 7750 permetting vlan 1 10 and 12. and G3/0/25 connected to second 7750 permetting the same vlans.



when is type dis stp brief for G1/0/26 and G3/0/25 i see that the G1/0/26 is master port for all stp instance 1 and 2. and G3/0/25 is alternative.



is this phenomene normal?



regards

[Shirin]

Is 4500 stacked ?

If yes then that could be the reason. If stacked I think that this switch can not have both uplinks forwarding. Call 3Com support and let us know.