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## Packet Mirroring Overview

Packet mirroring enables you to automatically send a copy of a packet to an external host for analysis. Packet mirroring has many uses, including traffic debugging and troubleshooting user networking problems.

The JUNOSe software provides two methods that you can use to configure and manage your packet-mirroring environment—CLI-based and RADIUS-based.

- CLI-based packet mirroring—An authorized operator uses the router’s CLI commands to configure and manage packet mirroring. You can mirror traffic related to a specific IP, IPv6, or L2TP interface or traffic related to a particular user. You also use CLI commands to create secure policies that identify the traffic to be mirrored and specify how the mirrored traffic is treated.
- RADIUS-based packet mirroring—A RADIUS administrator uses RADIUS attributes to configure packet mirroring of a particular user’s traffic. The router creates dynamic secure policies for the mirroring operation.

In both the CLI-based and the RADIUS-based packet mirroring methods, the original traffic is sent to its intended destination and the mirrored traffic is sent to an analyzer (the mediation device). The mirroring operations are transparent to the user whose traffic is being mirrored.

| Note: Packet-mirroring operations require some system resources. To avoid performance degradation, limit the amount of mirrored traffic to a maximum of 5 percent of the E-series router’s total traffic.

Packet mirroring is supported on ASIC-based modules. See ERX Module Guide, Appendix A, Module Protocol Support for information about modules supported on ERX routers. See E120 and E320 Module Guide, Appendix A, IOA Protocol Support for information about modules supported on the E120 and E320 routers.

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