Policy Framework Configuration Guide - Juniper Networks

Chapter 15: Traffic Forwarding and Monitoring Configuration
Associating a Port-Mirroring Instance on M120 Routers
To associate a port-mirroring instance with a FEB on an M120 router, include the
port-mirror-instance port-mirroring-instance-name statement at the [edit chassis feb
slot-number] hierarchy level:
[edit chassis]
feb slot-number {
port-mirror-instance port-mirroring-instance-name;
}
For slot-number, specify the slot number of the FEB you want to associate with the
port-mirroring instance. For port-mirroring-instance-name, specify the name of a
port-mirroring instance you configured at the [edit forwarding-options port-mirroring]
hierarchy level. For information about configuring FEB redundancy on an M120 router,
see the Junos High Availability Configuration Guide. For information about configuring
FPC-to-FEB connectivity on an M120 router, see the Junos System Basics Configuration
Guide.
Configuring MX Series Ethernet Services Routers and M120 Routers to Mirror
Traffic Only Once
On MX Series and M120 routers only, you can configure port mirroring so that the router
mirrors traffic only once. If you configure port mirroring on both ingress and egress
interfaces, the same packet could be mirrored twice. To mirror packets only once and
prevent the router from sending duplicate sampled packets to the same mirroring
destination, include the mirror-once statement at the [edit forwarding-options
port-mirroring] hierarchy level:
[edit forwarding-options port-mirroring]
mirror-once;
NOTE: The mirror-once statement is supported only in the global
port-mirroring instance.
Configuring Packet Capture
Packet capture allows you to monitor and analyze offline IP version 4 (IPv4) packets
flowing through a router. Packet capture monitors packet fragments also. Packet capture
can be enabled on any interface and can analyze ingress traffic, egress traffic, or both.
NOTE: Packet capture is supported for the J Series Services Routers only.
Packet capture is not supported on tunnel interfaces. You cannot configure
packet capture and sampling at the same time.
To configure packet capture, include the packet-capture statement at the [edit
forwarding-options] hierarchy level:
[edit forwarding-options]
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