Configuring Port Mirroring Instances on MX-series Routers

You can configure port mirroring for Layer 2 VPLS traffic on MX-series routers. To configure port mirroring, include the vpls statement at the [edit forwarding-options port-mirroring] hierarchy level.

You can configure multiple instances of port mirroring to enable multiple Packet Forwarding Engines to mirror packets to different destinations. To configure multiple instances, include the instance instance-name statement at the [edit forwarding-options port-mirroring] hierarchy level.

To configure a router to sample the packet for port mirroring only once, include the mirror-once statement at the [edit forwarding-options]. This option is useful when you are performing port mirroring on both the ingress and egress interfaces to eliminate duplication when input and output filtering is performed on the same packet.

Configuring Port Mirroring Instances at the DPC Level on MX-series Routers

To bind a port-mirroring instance to a specific DPC and its Packet Forwarding Engines, include the port-mirror-instance instance-name statement at the [edit chassis fpc number] hierarchy level. A port-mirror instance configured at the FPC-level for the DPC is bound to all the Packet Forwarding Engines on the DPC. This overrides the global port mirroring properties (if the port-mirroring statement has been included at the [edit forwarding-options] hierarchy level).

Configuring Port Mirroring Instances at the PIC Level on MX-series Routers

For MX-series routers, there is a one-to-one mapping of the Packet Forwarding Engines and the PICs. Therefore, you can override the port mirroring instance properties configured at the DPC level and configure a PIC-level port-mirroring instance. To bind a port mirroring instance to a specific Packet Forwarding Engine and its associated ports, include the include the port-mirror-instance pm-instance-name statement at the [edit chassis fpc slot-number pic number] hierarchy level.

Precedence of Port-Mirroring Instances at Different Levels of the Chassis

If port-mirroring instances are configured at multiple levels in the MX-series router hierarchy, the port-mirroring properties are applied as follows:

1. For chassis-level Layer 2 port mirroring, configured by including the port-mirroring statement at the [edit forwarding-options] hierarchy level, the global port-mirroring properties apply to all DPCs and their Packet Forwarding Engines and their associated ports.
2. For a DPC bound to a named port-mirroring instance, configured by including the port-mirror-instance pm-instance-name statement at the [edit chassis fpc slot-number] hierarchy level, the FPC-level port mirroring properties apply to all Packet Forwarding Engines (and their associated ports) on the DPC and override the properties of the global port-mirroring instance (if the port-mirroring statement has been included at the [edit forwarding-options] hierarchy level).
3. For a Packet Forwarding Engine bound to a Layer 2 port-mirroring instance (configured by including the port-mirror-instance pm-instance-name-b statement at the [edit chassis fpc slot-number pic slot-number] hierarchy level), the PIC-level port-mirroring properties apply to all ports associated with the Packet Forwarding Engine and override the properties bound to the DPC (if the port-mirror-instance pm-instance-name-a statement has been included at the [edit chassis fpc slot-number] hierarchy level).

For more information about configuring port mirroring for Layer 2 VPLS traffic, see the JUNOS MX-series Layer 2 Configuration Guide.

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