Cisco 3845 Software Guide - Page 237

Chapter 11 Configuring Ethernet Virtual Connections (EVCs) Configuring EFPs Bridge Domains and VLAN Encapsulation Unlike VLANs, the bridge-domain number does not need to match the VLAN encapsulation number. Switch (config)# interface gigabitethernet0/1 Switch (config-if)# service instance 1 Ethernet Switch (config-if-srv)# encapsulation dot1q 10 Switch (config-if-srv)# bridge-domain 8000 Switch (config)# interface gigabitethernet0/2 Switch (config-if)# service instance 1 Ethernet Switch (config-if-srv)# encapsulation dot1q 10 Switch (config-if-srv)# bridge-domain 8000 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. Switch (config)# interface gigabitethernet0/1 Switch (config-if)# service instance 1 Ethernet Switch (config-if-srv)# encapsulation dot1q 10 Switch (config-if-srv)# bridge-domain 8000 Switch (config)# interface gigabitethernet0/2 Switch (config-if)# service instance 1 Ethernet Switch (config-if-srv)# encapsulation dot1q 99 Switch (config-if-srv)# bridge-domain 8000 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). Switch (config)# interface gigabitethernet0/1 Switch (config-if)# service instance 1 Ethernet Switch (config-if-srv)# encapsulation dot1q 10 Switch (config-if-srv)# rewrite ingress tag pop 1 symmetric Switch (config-if-srv)# bridge-domain 8000 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 8000 since no other service instance in bridge domain 8000 is in split-horizon group 2. Service instance 4 can forward traffic to any service instance in bridge domain 8000 since it has not joined any split-horizon groups. Switch (config)# interface gigabitethernet0/1 Switch (config-if)# service instance 1 Ethernet Switch (config-if-srv)# encapsulation dot1q 10 Switch (config-if-srv)# rewrite ingress pop 1 symmetric Switch (config-if-srv)# bridge-domain 8000 split-horizon group 1 Switch (config-if-srv)# exit Switch (config-if)# service instance 2 Ethernet Switch (config-if-srv)# encapsulation dot1q 99 Switch (config-if-srv)# rewrite ingress pop 1 symmetric Switch (config-if-srv)# bridge-domain 8000 split-horizon group 1 Switch (config)# interface gigabitethernet0/2 OL-23400-01 Cisco ME 3800X and 3600X Switch Software Configuration Guide 11-11