Reference Guide

Session and VLAN requirements
Remote port mirroring requires a source session (monitored ports on dierent source devices), a reserved tagged VLAN for transporting
mirrored trac (congured on source, intermediate, and destination devices), and a destination session (destination ports connected to
analyzers on destination devices).
• Congure any network device with source ports and destination ports and enable it to function in an intermediate transport session for
a reserved VLAN at the same time for multiple remote-port mirroring sessions. Enable and disable individual mirroring sessions.
• BPDU monitoring is not required to use remote port mirroring.
• A remote port mirroring session mirrors monitored trac by prexing the reserved VLAN tag to monitored packets to copy to the
reserved VLAN.
• The source address, destination address, and original VLAN ID of the mirrored packet are prexed with the tagged VLAN header.
Untagged source packets are tagged with the reserved VLAN ID.
• The member port of the reserved VLAN must have the MTU and IPMTU value as MAX+4 (to hold the VLAN tag parameter).
• To associate with source session, the reserved VLAN can have a maximum of four member ports.
• To associate with destination session, the reserved VLAN can have multiple member ports.
• The reserved VLAN cannot have untagged ports.
Reserved L2 VLAN
• MAC address learning in the reserved VLAN is automatically disabled.
• You can automatically congure the reserved VLAN for remote port mirroring on intermediate devices by using GVRP.
• There is no restriction on the VLAN IDs used for the reserved remote-mirroring VLAN. Valid VLAN IDs are from 2 to 4094. The default
VLAN ID is not supported.
• In mirrored trac, packets that have the same destination MAC address as an intermediate or destination device in the path used by
the reserved VLAN to transport the mirrored trac are dropped by the device that receives the trac if the device has a L3 VLAN
congured.
Source session
• Congure physical ports and port-channels as sources in remote port mirroring and use them in the same source session. You can use
both L2 (congured with the switchport command) and L3 ports as source ports. Optionally congure one or more source VLANs
to congure the VLAN trac to be mirrored on source ports.
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