Specifications

Optimizing Performance
88
EIO0000000051 6/2010
Port Mirroring
Introduction
Port mirroring lets you troubleshoot switch port transmissions by copying the traffic
that passes through one port (the source or mirrored port) and sending the copied
transmission to a second port (the destination or mirror) port, where the packets can
be examined.
In the following example, the data packets transmitted over port 1 are copied and
sent to port 6. To troubleshoot port 1, a PC with packet sniffing software is used to
analyze the traffic on port 6 and thereby troubleshoot port 1.
A target device of port 1 transmissions
B PC with packet sniffing software connected to port 6, which mirrors port 1 transmissions
Port mirroring does not affect the normal forwarding behavior of the mirrored port. In
most switches, you can configure port mirroring so that you can forward and
examine:
z only the incoming packets of a single mirrored port
z only the outgoing packets of a single mirrored port
z both the incoming and outgoing packets of a single mirrored port
z the packets of several mirrored ports—or the whole switch
A packet sniffer’s troubleshooting features should include:
z analyzing network problems
z monitoring network activity