Administrator Guide
30 Dell Campus Networking Interoperability with Cisco Catalyst 1.1 | version 1.1
2.7.1 Configuring MST — Dell N-Series
The configuration below is for both Dell switches, N3024-1 and N3024-2. The mst instance priority value on
each mst instance for each switch determines STP root priority, where the lower the value the higher the
priority for selection. This setting ensures that the respective switch becomes the root for that MST instance.
The default priority is 32768. For example, setting the MST 1 priority to 4096 on the first switch ensures that
switch becomes the root for the MST 1 instance. Likewise, setting the MST 2 priority to 4096 on the second
switch ensures that switch becomes the root for MST 2 instance. Setting the opposing MST instance priority
to a value of 16384 ensures the partner switch will be the backup in the topology. MST instance VLANs,
name and revision values must be identical across participating switches. Once the configuration is complete
the command show spanning-tree instance n, where n represents instance ID can be issued to verify
VLAN participation and port state.
N3024-1#configure
N3024-1(config)#spanning-tree mst configuration
N3024-1(config-mst)#instance 1 add vlan 30-32
N3024-1(config-mst)#instance 2 add vlan 33-35
N3024-1(config-mst)#name Region1
N3024-1(config-mst)#revision 1
N3024-1(config-mst)#exit
N3024-1(config)#spanning-tree mst 1 priority 4096
N3024-1(config)#spanning-tree mst 2 priority 16384
N3024-1(config)#spanning-tree mode mst
N3024-1(config)#exit
N3024-2#configure
N3024-2(config)#spanning-tree mst configuration
N3024-2(config-mst)#instance 1 add vlan 30-32
N3024-2(config-mst)#instance 2 add vlan 33-35
N3024-2(config-mst)#name Region1
N3024-2(config-mst)#revision 1
N3024-2(config-mst)#exit
N3024-2(config)#spanning-tree mst 1 priority 16384
N3024-2(config)#spanning-tree mst 2 priority 4096
N3024-2(config)#spanning-tree mode mst
N3024-2(config)#exit
N3024-1#show spanning-tree instance 1 | exclude DIS
Spanning Tree: Enabled BPDU Flooding: Disabled Portfast BPDU Filtering:
Disabled
Mode: mst
CST Regional Root: 10:00:68:EF:BD:EA:B1:80
Regional Root Path Cost: 0
###### MST 1 Vlan Mapped: 30-32
ROOT ID
Priority 4096
Address 001E.C9DE.D11A