Chapter 6
ATX Port Mirroring
Using Port MIrroring; configuring port mirroring locally; configuring port mirroring remotely
The Port Mirroring utility allows you to capture network traffic appearing on one or more of the ATX’s ports, and to reproduce that traffic on a designated “diagnostic” port for monitoring purposes. The diagnostic port may be another of the ATX’s ports (Ethernet, Token Ring, or FDDI), or a remote port on another ATX in your network.
The Port Mirroring window (Figure
Port mirroring introduces a certain amount of latency to the switch’s traffic, depending upon the load at the mirrored ports, the types of packets being captured, and whether the diagnostic port is local or remote. To remedy this situation, you can establish “mirror filters” using the ATX’s Port Filtering utility. Mirror filters are especially helpful when you are using a remote diagnostic port, since the physical connection to the remote port imposes bandwidth constraints on the mirrored traffic. Using a mirror filter you can restrict the amount of monitored traffic by filtering inbound or outbound packets according to source and destination addresses, vendors, types, and frame protocols. You can also filter out packets based on a designated portion of their data field. Mirror filters can also be used when you are using a local diagnostic port, if necessary. See Chapter 4, Using ATX Port Filtering, for details on defining mirror filters.
The Port mirroring window also allows you to discard or truncate oversized packets when using a local diagnostic port.
NOTE |
When mirroring traffic to a remote diagnostic port, the mirrored packets are encapsulated and routed to the specified port. Oversized packets are segmented during this process, and therefore do not need to be discarded or truncated.
