Cisco 3845 - Security Bundle Router Software Manual page 252
Software configuration guide
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Chapter 11
Configuring Ethernet Virtual Connections (EVCs)
Configuring Other Features on EFPs
Switch (config)# interface gigabitethernet0/2
Switch (config-if)# switchport mode trunk
Switch (config-if)# switchport allowed vlan none
Switch (config-if)# service instance 1 Ethernet
Switch (config-if-srv)# encapsulation dot1q 3000
Switch (config-if-srv)# rewrite ingress tag pop 1 symmetric
Switch (config-if-srv)# bridge-domain 20
Switch (config-if-srv)# exit
Switch (config-if)# service instance 2 Ethernet
Switch (config-if-srv)# encapsulation dot1q 3001
Switch (config-if-srv)# rewrite ingress tag pop 1 symmetric
Switch (config-if-srv)# bridge-domain 30
EVCs and switchports can exist simultaneously on the same switch. When an EFP joins a bridge domain
1 through 4095, it is part of the same flood domain as VLANs 1 through 4095. If an EFP uses a bridge
domain greater than or equal to 4096, it belongs to the EFP-only flood domain.
This example shows VLANs and EFPs sharing the same flooding domain.
Switch (config)# interface gigabitethernet0/1
Switch (config-if)# switchport mode trunk
Switch (config-if)# switchport allowed vlan 1000
Switch (config)# interface gigabitethernet0/2
Switch (config-if)# service instance 1 Ethernet
Switch (config-if-srv)# encapsulation dot1q 1000
Switch (config-if-srv)# bridge-domain 1000
When data packets are forwarded between EFPs and switchports, the EFP and switchport configurations
are applied to the packet. This removes the ambiguity of the tagging behavior between them.
The following illustrations show tagging behavior between an EFP and a switchport. A switchport trunk
has an implicit outer VLAN pop at ingress and an implicit outer VLAN push at egress. When rewrite is
enabled, a VLAN tag is popped at ingress and a VLAN tag corresponding to the bridge domain that
bridged the packet is pushed at egress on the switchport trunk without any explicit configuration. When
a VLAN tag is pushed on a packet egressing at the switchport, the VLAN ID corresponds to the
bridge-domain ID over which the packet is bridged.
Figure 11-6
to
Figure 11-8
show traffic between a switchport and an EFP when rewrite symmetric is
enabled on the EFP.
Figure 11-6
Single-tagged Traffic Between a Switchport and an EFP with Rewrite
VLAN tag
VLAN tag
Bridge domain
Service instance 1 ethernet
10
10
encapsulation dot1q10
10
Switchport trunk
rewrite ingress tag pop 1 symmetric
bridge-domain 10
In this example, for traffic entering the switchport trunk port, the VLAN tag is popped on ingress at the
switchport trunk port and the untagged packet is bridged over bridge domain 10. On egress, the rewrite
operation results in a VLAN tag (encapsulation dot1q 10) to be pushed (added), and the packet egresses
on the EFP with a single tag (VLAN l0).
Cisco ME 3800X and 3600X Switch Software Configuration Guide
11-26
OL-23400-01
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