Cisco Systems A9014CFD manual Example Rewrite, Example Split Horizon

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

	Cisco ASR 901 Series Aggregation Services Router Software Configuration Guide
OL-23826-09		8-11