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Enabling Passive Flow Monitoring

You can monitor IPv4 traffic from another router if you have the following components installed in an M40e, M160, M320, or T-series routing platform:

Monitoring Services, Adaptive Services, or MultiServices PICs to perform the service processing.
SONET/SDH, Fast Ethernet, or Gigabit Ethernet PICs as transit interfaces.

On SONET/SDH interfaces, you enable passive flow monitoring by including the passive-monitor-mode statement at the [edit interfaces interface-name unit logical-unit-number] hierarchy level:




passive-monitor-mode;

On Asynchronous Transfer Mode (ATM), Fast Ethernet, or Gigabit Ethernet interfaces, you enable passive flow monitoring by including the passive-monitor-mode statement at the [edit interfaces interface-name] hierarchy level:




passive-monitor-mode;

When you configure an interface in passive monitoring mode, the Packet Forwarding Engine silently drops packets coming from that interface and destined to the router itself. Passive monitoring mode also stops the Routing Engine from transmitting any packet from that interface. Packets received from the monitored interface can be forwarded to monitoring interfaces. If you include the passive-monitor-mode statement in the configuration:

The ATM interface is always up, and the interface does not receive or transmit incoming control packets, such as Operation, Administration, and Maintenance (OAM) and Interim Local Management Interface (ILMI) cells.
The SONET/SDH interface does not send keepalives or alarms, and does not participate actively on the network.
Gigabit and Fast Ethernet interfaces can support both per-port passive monitoring and per-VLAN passive monitoring. The destination MAC filter on the receive port of the Ethernet interfaces is disabled.
Ethernet encapsulation options are not allowed.

On monitoring services interfaces, you enable passive flow monitoring by including the family statement at the [edit interfaces interface-name unit logical-unit-number] hierarchy level, specifying the inet option:




family inet;

For the monitoring services interface, you can configure multiservice physical interface properties. For more information, see Configuring the Flow-Monitoring Interface.

For conformity with cflowd record structure, you must include the receive-options-packets and receive-ttl-exceeded statements at the [edit interfaces interface-name unit logical-unit-number family inet] hierarchy level:




receive-options-packets;

receive-ttl-exceeded;

For more information, see the following sections:

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