Cisco Systems A9014CFD Example: Rewrite , Example: Split Horizon

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Cisco ASR 901 Series Aggregation Services Router Software Configuration Guide
OL-23826-09
Chapter 8 Configuring Ethernet Virtual Connections
Configuration Examples of Supported Features
However, when encapsulations do not match in the same bridge domain, traffic cannot be forwarded. In
this example, the service instances on Gigabit Ethernet 0/1 and 0/2 can not forward between each other,
since the encapsulations don’t match (filtering criteria). However, you can use the rewrite command to
allow communication between these two.
Router (config)# interface gigabitethernet0/1
Router (config-if)# service instance 1 Ethernet
Router (config-if-srv)# encapsulation dot1q 10
Router (config-if-srv)# bridge-domain 4000
Router (config)# interface gigabitethernet0/2
Router (config-if)# service instance 1 Ethernet
Router (config-if-srv)# encapsulation dot1q 99
Router (config-if-srv)# bridge-domain 4000
Example: Rewrite
In this example, a packet that matches the encapsulation will have one tag removed (popped off). The
symmetric keyword allows the reverse direction to have the inverse action: a packet that egresses out
this service instance will have the encapsulation (VLAN 10) added (pushed on).
Router (config)# interface gigabitethernet0/1
Router (config-if)# service instance 1 Ethernet
Router (config-if-srv)# encapsulation dot1q 10
Router (config-if-srv)# rewrite ingress tag pop 1 symmetric
Router (config-if-srv)# bridge-domain 4000
Example: Split Horizon
In this example, service instances 1 and 2 cannot forward and receive packets from each other. Service
instance 3 can forward traffic to any service instance in bridge domain 4000 since it has not joined any
split-horizon groups.
Router (config)# interface gigabitethernet0/1
Router (config-if)# service instance 1 Ethernet
Router (config-if-srv)# encapsulation dot1q 10
Router (config-if-srv)# rewrite ingress pop 1 symmetric
Router (config-if-srv)# bridge-domain 4000 split-horizon group 1
Router (config-if-srv)# exit
Router (config)# interface gigabitethernet0/2
Router (config-if)# service instance 2 Ethernet
Router (config-if-srv)# encapsulation dot1q 99
Router (config-if-srv)# rewrite ingress pop 1 symmetric
Router (config-if-srv)# bridge-domain 4000 split-horizon group 1
Router (config-if-srv)# exit
Router (config)# interface gigabitethernet0/3
Router (config-if)# service instance 3 Ethernet
Router (config-if-srv)# encapsulation dot1q 99
Router (config-if-srv)# rewrite ingress pop 1 symmetric
Router (config-if-srv)# bridge-domain 4000
Router (config-if-srv)# exit