Monitoring Switch Traffic 455Configuring RSPANRSPAN supports the transport of mirrored packets across the network to aremote switch. Ports may be configured as source ports, intermediate ports, ordestination ports.RSPAN Source SwitchThis example mirrors interface gi1/0/3 to VLAN 723. VLAN 723 is theselected transit VLAN. Administrators should reserve a VLAN as the RSPANVLAN when designing their network. The source switch requires a reflectorport to carry packets to the transit switch. The reflector port must beconfigured as trunk port. Untagged packets on the source port are transmittedon the RSPAN VLAN tagged with the RSPAN VLAN. Tagged packets on thesource port are transmitted over the RPSAN VLAN double-tagged with theouter tag containing the RSPAN VLAN.The last line in this configuration enables the monitor session. It isrecommended that configuration proceed with the destination switch first,followed by the intermediate switches, and then by the source switch.1 Configure RSPAN on VLAN 723:console#configureconsole(config)#vlan 723console(config-vlan723)#remote-spanconsole(config-vlan723)#exit2 Configure interface te1/0/1 as the reflector port in trunk mode:console(config)#interface te1/0/1console(config-if-Te1/0/1)#switchport mode trunkconsole(config-if-Te1/0/1)#switchport trunkallowed vlan 723console(config-if-Te1/0/1)#exit3 Configure a mirroring session with a source port gi1/0/3, the destinationVLAN 723, and reflector port te1/0/1:console(config)# monitor session 1 sourceinterface gi1/0/3console(config)# monitor session 1 destinationremote vlan 723 reflector-port te1/0/1
