1-2Local Port MirroringIn local port mirroring, packets passing through one or more source ports of a device arecopied to the destination port on the same device for packet analysis and monitoring. Inthis case, the source ports and the destination port must be located on the same device.Remote Port MirroringRemote port mirroring does not require the source and destination ports to be on the samedevice. The source and destination ports can be located on multiple devices across thenetwork. This allows an administrator to monitor traffic on remote devices conveniently.To implement remote port mirroring, a special VLAN, called remote-probe VLAN, is used.All mirrored packets are sent from the reflector port of the source switch to the monitor porton the destination switch through the remote-probe VLAN. Figure 1-2 illustrates theimplementation of remote port mirroring.Figure 1-2 Remote port mirroring applicationThe switches involved in remote port mirroring function as follows:z Source switchThe source switch is the device where the monitored port is located. It copies trafficpassing through the monitored port to the reflector port. The reflector port then transmitsthe traffic to an intermediate switch (if any) or destination switch through the remote-probeVLAN.z Intermediate switchIntermediate switches are switches between the source switch and destination switch onthe network. An intermediate switch forwards mirrored traffic flows to the next intermediateswitch or the destination switch through the remote-probe VLAN. No intermediate switch ispresent if the source and destination switches directly connect to each other.z Destination switchThe destination switch is where the monitor port is located. The destination switchforwards the mirrored traffic flows it received from the remote-probe VLAN to themonitoring device through the destination port.
