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13-7
Cisco ASR 901 Series Aggregation Services Router Software Configuration Guide
OL-23826-09
Chapter 13 Configuring MST on EVC Bridge Domain
Contents
In this example, interface gi4/1 and interface gi4/3 are connected back-to-back. Each has a service
instance (EFP) attached to it. The EFP on both interfaces has an encapsulation VLAN ID of 2. Changing
the VLAN ID from 2 to 8 in the encapsulation directive for the EFP on interface gi4/1 stops the MSTP
from running in the MST instance to which the old VLAN is mapped and starts the MSTP in the MST
instance to which the new VLAN is mapped:
Router(config-if)# interface g4/1
Router(config-if)# service instance 1 ethernet
Router(config-if-srv)# encap dot1q 8
Router(config-if-srv)# end
Use this command to verify the configuration:
Router# show spanning-tree vlan 2
MST1
Spanning tree enabled protocol mstp
Root ID Priority 32769
Address 0009.e91a.bc40
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 0009.e91a.bc40
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Interface Role Sts Cost Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Gi4/3 Desg FWD 20000 128.1540 P2p
Router# show spanning-tree vlan 8
MST2
Spanning tree enabled protocol mstp
Root ID Priority 32770
Address 0009.e91a.bc40
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32770 (priority 32768 sys-id-ext 2)
Address 0009.e91a.bc40
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Interface Role Sts Cost Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Gi4/1 Desg FWD 20000 128.1537 P2p
In this example, interface gi4/3 (with an EFP that has an outer encapsulation VLAN ID of 2 and a bridge
domain of 100) receives a new service:
Router# enable
Router# configure terminal
Router(config)# interface g4/3
Router((config-if)# service instance 2 ethernet
Router((config-if-srv)# encap dot1q 2 second-dot1q 100
Router((config-if-srv)# bridge-domain 200
Now there are two EFPs configured on interface gi4/3 and both of them have the same outer VLAN 2.
interface GigabitEthernet4/3
no ip address
service instance 1 ethernet