Administrator Guide

Layer 2 Switching Commands 670
to RSPAN traffic only. Traffic on other VLANs on the reflector port is
forwarded normally. Each RSPAN session must use a unique reflector port
and RSPAN VLAN. Reflector ports should be configured as trunk or general
mode.
VLAN based mirroring is applicable only for ingress (RX) traffic.
For RSPAN, the original tag is not retained for tagged traffic
received/transmitted at the source port(s).
On ingress, the port mirroring logic stage is after the VLAN tag processing
stage in the hardware. This means that mirrored packets may not appear the
same as they do on the wire if VLAN tag processing occurs. Examples of
VLAN tag processing are DVLAN tunneling (QinQ) or VLAN rewriting.
Likewise, on egress, the port mirroring logic stage is before the VLAN tag
processing stage. This means that, on egress, packets may not appear as they
do on the wire if processing such as VLAN or CoS value rewriting is
programmed.
Reserve a few VLANs across your network for the exclusive use of RSPAN. Do
not assign access ports to these VLANs. Monitored traffic is forwarded within
the RSPAN VLAN to the reflector port on the source switch. On a source
switch, when both an RSPAN VLAN and reflector port are configured on a
trunk or general mode port with other VLANs, the interface can also carry
normal traffic on the other VLANs. For example, an uplink interface (trunk
port) can carry both the RSPAN traffic and other traffic. Do not configure the
RSPAN VLAN as a native VLAN. Be sure to remove the RSPAN VLAN from
ports on which mirrored traffic should not be carried.
The source VLAN (if configured), cannot be the same as the RSPAN VLAN.
The destination interface must be configured as a member of the RSPAN
VLAN on the source switch.
The source interface must be configured as a member of the RSPAN VLAN
on the destination switch.
If an ACL name is specified, the ACL must be created prior to its use in an
RSPAN configuration.
If neither rx, tx, nor both are specified in a source session, both ingress and
egress traffic are monitored.
RSPAN VLANs must be configured with the remote-span command prior to
configuration in an RSPAN session.
2CSNXXX_SWUM204.book Page 670 Monday, January 25, 2016 1:25 PM