O'Reilly logo

Juniper MX Series by Harry Reynolds, Douglas Richard Hanks Jr.

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

Port Mirroring

One of the most useful tools in the troubleshooting bag is port mirroring. It allows you to specify traffic with a firewall filter and copy it to another interface. The copied traffic can then be used for analysis or testing. One of the most interesting use cases I recall is when a customer wanted to test a firewall’s throughput on production data, but obviously not impact production traffic. Port mirroring was the perfect tool to match the production data and send a copy of the traffic to the firewall under test, while the original traffic was forwarded to its final destination on the production network.

Junos has supported port mirroring for a very long time, and the architecture is very simple and flexible. There are four major components that make up port mirroring, as shown in Figure 7-15: FPC, port mirroring instances, next-hop groups, and next-hops.

Port Mirroring Workflow.

Figure 7-15. Port Mirroring Workflow.

Port mirroring instances are associated with FPCs, and up to two port mirroring instances can be associated with a single FPC. This concept is similar to other Trio inline functions where the FPC is associated to an instance or inline service. The next component is a next-hop group; this is simply a collection of interfaces and associated next-hops. The use of a next-hop group is optional. The last components are the next-hops that reference a specific interface and next-hop.

However, ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required