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Chapter 8
Configuring IEEE 802.1Q Tunneling and Layer 2 Protocol Tunneling
To enable or disable Layer 2 protocol tunneling on a trunk port or a range of trunk ports, perform this
task in privileged mode:
Task
Enable or disable Layer 2 protocol tunneling on a
trunk.
Note
Do not configure (enable or disable) Layer 2 protocol tunneling on trunks when active Layer 2 protocol
tunnels are already configured. If you plan to configure Layer 2 protocol tunneling on trunks, make sure
that you do so before performing any other Layer 2 protocol tunneling tasks.
This example shows how to enable Layer 2 protocol tunneling on a trunk:
Console> (enable) set l2protocol-tunnel trunk enable
Layer 2 Protocol Tunnel on trunks is allowed.
Console> (enable)
This example shows how to disable Layer 2 protocol tunneling on a trunk:
Console> (enable) set l2protocol-tunnel trunk disable
Warning!! Clear any layer 2 protocol tunnel configuration on trunks
before using this command.
Layer 2 Protocol Tunnel on trunks is not allowed.
Console> (enable)
Layer 2 Protocol Tunneling on Trunks Example
The example in
ports (nontrunk) with 802.1Q tunneling configured and two trunk ports with Layer 2 protocol tunneling
configured.
Service provider A sends double-tagged encapsulated packets through the service provider cloud with
the expectation that the packets will be received in the same double-tagged format on the other end. If
customer switch 2 and customer switch 3 send single-tagged packets to service provider B, there is no
way to identify the VLAN at egress at service provider A. However, if all switches are sending
double-tagged packets, service provider A can correctly tunnel the packets at egress. To achieve correct
results, all packets that are received on Layer 2 protocol tunneling trunk ports must be double tagged.
Another example is when a customer wants to tunnel CDP and VTP packets. The CDP/VTP packets are
received by a Catalyst 6500 series switch from a third-party switch that is tunneled from other Cisco
switches. If the service provider wants to support multiple customers, the service provider must tunnel
CDP and VTP packets on a VLAN other than VLAN 1 because Catalyst 6500 series switches use VLAN
1 for transmitting CDP and VTP packets. Because the third-party switches should not directly connect
to Layer 2 protocol tunneling trunk ports, one of the third-party switches needs to do VLAN translation
or VLAN tagging to ensure that packets are tunneled on the correct VLAN.
OL-8978-04
Figure 8-2
shows a service provider network that includes Layer 2 protocol tunneling
Catalyst 6500 Series Switch Software Configuration Guide—Release 8.7
Configuring Layer 2 Protocol Tunneling on the Switch
Command
set l2protocol-tunnel trunk {enable | disable}
8-9
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Troubleshooting
