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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 Unsupported Features
Configuration Examples of Unsupported Features
• Example: Filtering
• Example: Overlapping Encapsulation
Example: 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.
Router (config)# interface gigabitethernet0/1
Router (config-if)# service instance 1 Ethernet
Router (config-if-srv)# encapsulation dot1q 20
Router (config-if-srv)# bridge-domain 19
Router (config)# interface gigabitethernet0/2
Router (config-if)# service instance 2 Ethernet
Router (config-if-srv)# encapsulation dot1q 30
Router (config-if-srv)# bridge-domain 19
Router (config)# interface gigabitethernet0/3
Router (config-if)# service instance 3 Ethernet
Router (config-if-srv)# encapsulation dot1q 10 second-dot1q 20
Router (config-if-srv)# rewrite ingress pop 1 symmetric
Router (config-if-srv)# bridge-domain 19
If a packet with VLAN tag 10 or 20 is received on Gigabit Ethernet 0/3, the ingress logical port would
be service instance 3. For the frame to be forwarded on a service instance, the egress frame must match
the encapsulation defined on that service instance after the rewrite is done. Service instance 1 checks for
outermost VLAN 20; service instance 2 checks for VLAN 30. In this example, the frame with VLAN
tags 10 and 20 can be sent to service instance 1 but not to service instance 2.
Example: Overlapping Encapsulation
The router does not allow overlapping encapsulation. Overlapping encapsulation configuration occurs
when two EFPs are configured on the same port and the same bridge domain and the set of
encapsulations on one EFP is a subset of the encapsulations on the other EFP.
Service instance 2 configuration is rejected because service instance 1 encapsulation dot1q any is
superset of service instance 2 encapsulation dot1q 10.
Router (config)# interface gigabitethernet 0/1
Router (config-if)# service instance 1 ethernet
Router (config-if-srv)# encapsulation dot1q any
Router (config-if-srv)# bridge-domain 10
Router (config-if-srv)# exit
Router (config-if)# service instance 2 ethernet
Router (config-if-srv)# encapsulation dot1q 10
Router (config-if-srv)# bridge-domain 10