Configuring External Ethernet Data Plane Loopback - Cisco 1941W Configuration Manual

Chapter Configuring Ethernet CFM and Y.1731 Performance Monitoring on Layer 3 Interfaces
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Configuring External Ethernet Data Plane Loopback

Configuring external Ethernet data plane loopback is permitted on a Layer 3 main interface and
subinterfaces.
Figure 1
Figure 1
Gi 0/0 Gi 0/0
Gi 0/0.1101 Gi 0/0.1101
customer 1101 customer 1101
vlan 1101 vlan 1101
Gi 0/0.1102 Gi 0/0.1102
customer 1102 customer 1102
vlan 1102 vlan 1102
The following steps show how to configure external Ethernet data plane loopback on a subinterface using
single and double tagging. (The procedure to configure external Ethernet data plane loopback on the
main interface is similar to this procedure.)
SUMMARY STEPS
enable
Step 1
configure terminal
Step 2
interface gigabitethernet slot/port.sub-port
Step 3
encapsulation dot1q vlan-id
Step 4
Cisco 3900 Series, Cisco 2900 Series, and Cisco 1900 Series Integrated Services Routers Generation 2 Software Configuration Guide
dot1ad is not supported on the main interface. However, untagged frames are supported on the main
interface.
Single VLAN is supported as a filtering option for a subinterface, but VLAN list and VLAN range
are not supported.
Only MAC address is supported as a filtering option for the main interface.
For the filtering option, the destination MAC cannot be combined with inner VLAN or outer VLAN.
There is no support for L3 and L4 loopback. Source and destination IP address or source and
destination ports will not be swapped.
Connectivity Fault Management (CFM) packets are transparent to the data plane loopback
configuration and cannot be looped back.
Packets coming from the other side of the wire where loopback is configured and having the same
destination MAC address are dropped.
The broadcast and multicast IP addresses of the broadcast and multicast IP frames that are received
cannot be used as the source IP address of the frame when it is sent back to the initiator. In such a
case, the IP address of the subinterface is used as the source IP address of the frame when it is sent
back to the initiator.
represents a sample topology to configure Ethernet data plane loopback.
Sample Topology
Router 1
Router 1
Gi 0/2 Gi 0/2
Gi 0/2.1101
Gi 0/2.1101
Provider Provider Carrier Carrier
vlan 100 vlan 100 vlan 10 vlan 10
Gi 0/2.1102 Gi 0/2.1102
Gi 0/2 Gi 0/2
Metro Ethernet Metro Ethernet
Gi 0/2.1101
Gi 0/2.1101
vlan 100 vlan 100
Gi 0/2.1102 Gi 0/2.1102
Ethernet Data Plane Loopback
Router 2
Router 2
Gi 0/0 Gi 0/0
Gi 0/0.1101 Gi 0/0.1101
customer 1101 customer 1101
vlan 1101 vlan 1101
Gi 0/0.1102 Gi 0/0.1102
customer 1102 customer 1102
vlan 1102 vlan 1102
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