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Software Configuration Guide—Release 15.0(2)SG
OL-23818-01
Chapter 51 Configuring SPAN and RSPAN Configuring RSPAN
Note You can apply an output access control list (ACL) to RSPAN traffic to selectively filter or monitor
specific packets. Specify these ACLs on the RSPAN VLAN in the RSPAN source switches.
RSPAN sessions can coexist with SPAN sessions within the limits described in the “SPAN and
RSPAN Session Limits” section on page 51-6.
For RSPAN configuration, you can distribute the source ports and the destination ports across
multiple switches in your network.
RSPAN does not support BPDU packet monitoring or other Layer 2 switch protocols.
The RSPAN VLAN is configured only on trunk ports and not on access ports. To avoid unwanted
traffic in RSPAN VLANs, make sure that all participating switches support the VLAN remote-span
feature. Access ports on the RSPAN VLAN are silently disabled.
You should create an RSPAN VLAN before configuring an RSPAN source or destination session.
If you enable VTP and VTP pruning, RSPAN traffic is pruned in the trunks to prevent the unwanted
flooding of RSPAN traffic across the network for VLAN-IDs that are lower than 1005.
Because RSPAN traffic is carried across a network on an RSPAN VLAN, the original VLAN
association of the mirrored packets is lost. RSPAN can only support forwarding of traffic from an
IDS device onto a single user-specified VLAN.
Creating an RSPAN Session
First create an RSPAN VLAN that does not exist for the RSPAN session in any of the switches that
participate in RSPAN. With VTP enabled in the network, you can create the RSPAN VLAN in one
switch, and then VTP propagates it to the other switches in the VTP domain for VLAN-IDs that are lower
than 1005.
Use VTP pruning to get efficient flow of RSPAN traffi c, or manual ly delet e the RSPAN VLAN from all
trunks that do not need to carry the RSPAN traffic.
To start an RSPAN source session and to specify the source (monitored) ports and the destination RSPAN
VLAN, perform this task:
Command Purpose
Step 1 Switch# configure terminal Enters global configuration mode.
Step 2 Switch(config)# no monitor session
{session_number | all | local | remote}Clears any existing RSPAN configuration for the session.
For session_number, specifies the session number identified with this
RSPAN session (1 through 6).
Specifies all to remove all RSPAN sessions, local to remov e all local
sessions, or remote to remove all remote SPAN sessions.
Step 3 Switch(config)# vlan {remote_vlan_ID} Specifies a remote VLAN ID.
Ensure that the VLAN ID is not being used for any user traffic.
Step 4 Switch(config-vlan)# remote-span Converts the VLAN ID to a remote VLAN ID.
Step 5 Switch(config-vlan)# exit Returns to global configuration mode.