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Configuring RSPAN
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Configuring RSPAN
The first step in configuring an RSPAN session is to select an RSPAN VLAN for the RSPAN session that
does not exist in any of the switches that will participate in RSPAN. With VTP enabled in the network,
you can create the RSPAN VLAN in one switch and VTP propagates it to the other switches in the VTP
domain.
Use VTP pruning to get efficient flow of RSPAN traffic, or manually delete the RSPAN VLAN from all
trunks that do not need to carry the RSPAN traffic.
Once the RSPAN VLAN is created, you configure the source and destination switches using the set
rspan command.
Software Configuration Guide—Catalyst 4000 Family, Catalyst 2948G, Catalyst 2980G, Releases 6.3 and 6.4
25-10
For RSPAN, trunking is required if you have a source switch with all source ports in one VLAN
(VLAN 2, for example) and it is connected to the destination switch through an uplink port that is
also in the same VLAN. With RSPAN, the traffic is forwarded to remote switches in the RSPAN
VLAN. The RSPAN VLAN is configured only on trunk ports, not on access ports.
The learning option applies to RSPAN destination ports only.
RSPAN does not support BPDU packet monitoring.
RSPAN VLANs are not included as sources for port-based RSPAN sessions when source trunk ports
have active RSPAN VLANs. Additionally, RSPAN VLANs cannot be sources in VSPAN sessions.
You can configure any VLAN as an RSPAN VLAN as long as these conditions are met:
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The same RSPAN VLAN is used for an RSPAN session in all the switches.
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All participating switches have appropriate hardware and software.
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No access port (including the sc0 interface) is configured in the RSPAN VLAN.
If you enable VLAN Trunk Protocol (VTP) and VTP pruning, RSPAN traffic is pruned in the trunks
to prevent the unwanted flooding of RSPAN traffic across the network.
If you enable GARP VLAN Registration Protocol (GVRP) and GVRP requests conflict with existing
RSPAN VLANs, you might observe unwanted traffic in the respective RSPAN sessions.
You can use RSPAN VLANs in Inter-Switch Link (ISL) to map dot1q. However, ensure that the
special properties of RSPAN VLANs are supported in all the switches to avoid unwanted traffic in
these VLANs.
Incoming traffic on the RSPAN destination port is disabled by default. You can enable it using the
inpkts enable keywords. However, while the port receives traffic for its assigned VLAN, it does not
participate in spanning tree for that VLAN. To avoid creating spanning tree loops with incoming
traffic enabled, assign the RSPAN destination port to an unused VLAN.
When the inpkts option is enabled, you can prevent the switch from learning source MAC addresses
from traffic received on the RSPAN destination port using the learning disable keywords. If you
want the switch to learn source MAC addresses from traffic received on the RSPAN destination port,
use the learning enable keywords. By default, the switch learns source MAC addresses from
incoming traffic (learning enable) if the inpkts option is enabled. The source MAC address
learning options only affect traffic received from a device attached to the RSPAN destination port
itself, not from traffic mirrored from the RSPAN source.
Chapter 25
Configuring SPAN and RSPAN
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