Remote Port MirroringRemote port mirroring does not require the source and destination ports to be on the same device. Thesource and destination ports can be located on multiple devices across the network. This allows anadministrator to monitor traffic on remote devices conveniently.To implement remote port mirroring, a special VLAN, called remote-probe VLAN, is used. All mirroredpackets are sent from the reflector port of the source switch to the monitor port on the destination switchthrough the remote-probe VLAN. Figure 46-2 illustrates the implementation of remote port mirroring.Figure 46-2 Remote port mirroring applicationReflector PortSource Port Trunk Port Destination PortRemote-probe VLANIntermediate SwitchSourceSwitch DestinationSwitchThe 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 traffic passing through themonitored port to the reflector port. The reflector port then transmits the traffic to an intermediate switch(if any) or destination switch through the remote-probe VLAN.z Intermediate switchIntermediate switches are switches between the source switch and destination switch on the network.An intermediate switch forwards mirrored traffic flows to the next intermediate switch or the destinationswitch through the remote-probe VLAN. No intermediate switch is present if the source and destinationswitches directly connect to each other.z Destination switchThe destination switch is where the monitor port is located. The destination switch forwards the mirroredtraffic flows it received from the remote-probe VLAN to the monitoring device through the destinationport.Table 46-1 describes how the ports on various switches are involved in the mirroring operation.Table 46-1 Ports involved in the mirroring operationSwitch Ports involved FunctionSource portPort monitored. It copies packets to the reflector portthrough local port mirroring. There can be more thanone source port.Reflector port Receives packets from the source port andbroadcasts the packets in the remote-probe VLAN.Source switchTrunk port Sends mirrored packets to the intermediate switchor the destination switch.46-2
