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Understanding Layer 2 Port Mirroring of PE Router Aggregated Ethernet Interfaces

 

An aggregated Ethernet interface is a virtual aggregated link that consists of a set of physical interfaces of the same speed and operating in full-duplex link connection mode. You can configure aggregated Ethernet interfaces between CE devices and PE routers for VPLS routing instances. Traffic is load-balanced across all of the links in the aggregated interface. If one or more links in the aggregated interface fails, the traffic is switched to the remaining links.

You can apply a Layer 2 port-mirroring firewall filter to an aggregated Ethernet interface to configure port-mirroring at the parent interface. However, if any child interfaces are bound to different Layer 2 port-mirroring instances, packets received at the child interfaces will be mirrored to the destinations specified by their respective port-mirroring instances. Thus, multiple child interfaces can mirror packets to multiple destinations.

For example, suppose the parent aggregated Ethernet interface instance ae0 has two child interfaces:

  • xe-2/0/0

  • xe-3/1/2

Suppose that these child interfaces on ae0 are bound to two different Layer 2 port-mirroring instances:

  • pm_instance_A—A named instance of Layer 2 port-mirroring, bound to child interface xe-2/0/0.

  • pm_instance_B—A named instance of Layer 2 port-mirroring, bound to child interface xe-3/1/2.

Now suppose you apply a Layer 2 port-mirroring firewall filter to the Layer 2 traffic sent on ae0.0 (logical unit 0 on the aggregated Ethernet interface instance 0). This enables port mirroring on ae0.0, which has the following effect on the processing of traffic received on the child interfaces for which Layer 2 port-mirroring properties are specified:

  • The packets received on xe-2/0/0 are mirrored to the output interfaces configured in port-mirroring instance pm_instance_A.

  • The packets received on xe-3/1/2.0 are mirrored to the output interfaces configured in port-mirroring instance pm_instance_B.

Because pm_instance_A and pm_instance_B can specify different packet-selection properties or mirror destination properties, the packets received on xe-2/0/0 and xe-3/1/2.0 can mirror different packets to different destinations.