Hairpinning; Egress Filtering - Cisco 3845 - Security Bundle Router Software Manual

Configuring EFPs
Switch (config-if)# service instance 3 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 2
Switch (config-if-srv)# exit
Switch (config-if)# service instance 4 Ethernet
Switch (config-if-srv)# encapsulation dot1q 99
Switch (config-if-srv)# rewrite ingress pop 1 symmetric
Switch (config-if-srv)# bridge-domain 8000

Hairpinning

The switch supports hairpinning, which refers to traffic ingressing and egressing same interface. To
achieve haripinning, configure two EFPs in the same bridge domain on the same physical interface, as
in this example.
Switch (config)# interface gigabitethernet0/2
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 5000
Switch (config-if-srv)# exit
Switch (config-if)# service instance 2 Ethernet
Switch (config-if-srv)# encapsulation dot1q 20
Switch (config-if-srv)# rewrite ingress tag pop 1 symmetric
Switch (config-if-srv)# bridge-domain 5000

Egress Filtering

In EVC switching, egress filtering is performed before the frame is sent on the egress EFP. Egress
filtering ensures that when a frame is sent, it conforms to the matching criteria of the service instance
applied on the ingress direction. EFP does not require egress filtering if the number of pops is the same
as the number of VLANs specified in the encapsulation command.
Note Specifying the cos keyword in the encapsulation command is relevant only in the ingress direction. For
egress filtering, cos is ignored.
For example, consider the following configuration.
Switch (config)# interface gigabitethernet0/1
Switch (config-if)# service instance 1 Ethernet
Switch (config-if-srv)# encapsulation dot1q 20
Switch (config-if-srv)# bridge-domain 19
Switch (config)# interface gigabitethernet0/2
Switch (config-if)# service instance 2 Ethernet
Switch (config-if-srv)# encapsulation dot1q 30
Switch (config-if-srv)# bridge-domain 19
Switch (config)# interface gigabitethernet0/3
Switch (config-if)# service instance 3 Ethernet
Switch (config-if-srv)# encapsulation dot1q 10 second-dot1q 20
Switch (config-if-srv)# rewrite ingress pop 1 symmetric
Switch (config-if-srv)# bridge-domain 19
Cisco ME 3800X and 3600X Switch Software Configuration Guide
11-12
Chapter 11 Configuring Ethernet Virtual Connections (EVCs)
OL-23400-01