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MST and instance configuration [7:87240] posted 04/14/2004
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I am running an MST interoperability test between a 3com 7700 and Cisco 6500
but I am not having much luck in getting it to work. What I am trying to
achieve is balanced traffic across two vlans which have been configured has
MST instance 1 and 2 (see below for full config commands used.

It is my understanding that with STP there should only ever be one Root
Bridge in a STP topology, however I am seeing two with both the Cisco and
3com devices claiming to be the Root Bridge.

I would be interested to hear from anyone who has any exposure to MST
configuration in either a multi-vendor or Cisco only environment.

I have also been trying to find out some more information about the
"Configuration Digest Signature Key" which is used in MST. I know it is a
type of HMAC-MD5 encryption facility, but I have no idea about its working
in and MST environment. Any help, which can be offered on this matter, would
also be gratefully accepted



Cisco Config

spanning-tree mode mst
no spanning-tree optimize bpdu transmission
spanning-tree mst configuration
 name Test
 instance 1 vlan 3
 instance 2 vlan 4

interface GigabitEthernet3/1
 no ip address
 switchport access vlan 3
interface GigabitEthernet3/2
 no ip address
 switchport access vlan 4

3com config

stp timer forward-delay 700
 stp timer max-age 1000
 stp enable
stp region-configuration
 region-name Test
 instance 1 vlan 3
 instance 2 vlan 4
 active region-configuration

interface GigabitEthernet3/0/1
 port access vlan 3
interface GigabitEthernet3/0/2
 port access vlan 4

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