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The router must use its loopback or OOB management interface address as the source address when originating NetFlow traffic.

Finding ID
Rule ID
Group Title
Netflow traffic is not using loopback address.
Target Key

Using a loopback address as the source address offers a multitude of uses for security, access, management, and scalability of routers. It is easier to construct appropriate ingress filters for router management plane traffic destined to the network management subnet since the source addresses will be from the range used for loopback interfaces instead of a larger range of addresses used for physical interfaces. Log information recorded by authentication and syslog servers will record the router’s loopback address instead of the numerous physical interface addresses. Netflow messages sent to management servers should use the loopback address as the source address.

Fix Text

Configure the router to use its loopback or OOB management interface address as the source address when originating NetFlow traffic.

Check Content

Review the configuration and verify the loopback interface address is used as the source address when originating Netflow traffic. If the device is managed from an OOB management network, the OOB interface must be used instead Step 1: Verify that a loopback address has been configured with an IP address. The configuration should look similar to the following. interfaces { lo0 { unit 0 { family inet { address; } } } Note: Only one loopback interface can be configured on Juniper routers; however, multiple addresses can be defined. Step 2: Juniper has adopted the Cisco PDU format for flow export; However, Juniper does not call it NetFlow but "cflowd" and uses the flow export concept as a means to export packet-sampling data. Juniper has a filtering mechanism which allows you to sample packets and log them to the local file system or they can be exported using the "cflowd" forwarding options. You should find a configuration similar to the example below depicting the source address for cflowd: forwarding-options { sampling { input { family inet { rate 100; run-length 4; max-packets-per-second 5000; } } output { cflowd { port 9991; source-address; } } } Note: If source-address is not specified, then the default-address-selection under system hierarchy must be configured. Configuring system default-address-selection will enable the router to use the loopback interface as the source address for most locally generated IP packets. This configuration would appear as follows: system { default-address-selection; … } }


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