Remote Port MirroringWhile local port monitoring allows you to monitor traffic from one or more source ports by directing it toa destination port on the same switch/router, remote port mirroring allows you to monitor Layer 2 andLayer 3 ingress and/or egress traffic on multiple source ports on different switches and forward themirrored traffic to multiple destination ports on different switches.Remote port mirroring helps network administrators monitor and analyze traffic to troubleshoot networkproblems in a time-saving and efficient way.In a remote-port mirroring session, monitored traffic is tagged with a VLAN ID and switched on a user-defined, non-routable L2 VLAN. The VLAN is reserved in the network to carry only mirrored traffic, whichis forwarded on all egress ports of the VLAN. Each intermediate switch that participates in the transport ofmirrored traffic must be configured with the reserved L2 VLAN. Remote port monitoring supportsmirroring sessions in which multiple source and destination ports are distributed across multiple switchesRemote Port Mirroring ExampleRemote port mirroring uses the analyzers shown in the aggregation network in Site A.The VLAN traffic on monitored links from the access network is tagged and assigned to a dedicated L2VLAN. Monitored links are configured in two source sessions shown with orange and green circles. Eachsource session uses a separate reserved VLAN to transmit mirrored packets (mirrored source-sessiontraffic is shown with an orange or green circle with a blue border).The reserved VLANs transport the mirrored traffic in sessions (blue pipes) to the destination analyzers inthe local network. Two destination sessions are shown: one for the reserved VLAN that transportsorange-circle traffic; one for the reserved VLAN that transports green-circle traffic.Port Monitoring 683
