Cisco Catalyst 3750 Metro Command Reference Manual page 254

l2protocol-tunnel
Defaults The default is that no Layer 2 protocol packets are tunneled.
If you enter the command with no keyword, the default is to tunnel CDP, LLDP, STP, and VTP packets.
If you enable point-to-point protocol tunneling with no keyword is entered, tunneling is enabled for all
three point-to-point protocols.
The default is to have no shutdown threshold for the number of Layer 2 protocol packets.
The default is to have no drop threshold for the number of Layer 2 protocol packets.
Command Modes
Interface configuration
Command History Release
12.1(14)AX
12.1(14)AX1
12.2(58)SE
Usage Guidelines
You must enter this command, with or without protocol types, to tunnel Layer 2 protocol packets.
Layer 2 protocol tunneling across a service-provider network ensures that Layer 2 protocol information
is propagated across the network to all customer locations. When protocol tunneling is enabled, protocol
packets are encapsulated with a well-known Cisco multicast address for transmission across the network.
When the packets reach their destination, the well-known MAC address is replaced by the Layer 2
protocol MAC address.
When Layer 2 protocol tunneling is enabled on ingress ports on a switch, egress trunk ports forward the
tunneled packets with a special encapsulation. If you also enable Layer 2 protocol tunneling on the
egress trunk port, this behavior is bypassed and the switch forwards control protocol data units (PDUs)
without any processing or modification. The Layer 2 protocol-tunnel bypass feature can provide
interoperability with third-party vendors. Bypass mode transparently forwards control PDUs to vendor
switches that have different ways of controlling protocol tunneling.
You can enable Layer 2 protocol tunneling individually for CDP, LLDP, STP, VTP, or for all these
protocols.
You can enable Layer 2 protocol tunneling on ports that are configured as access ports, 802.1Q tunnel
ports, or trunk ports. You cannot enable Layer 2 protocol tunneling on ports configured with switchport
mode dynamic auto or dynamic desirable.
EtherChannel port groups are compatible with tunnel ports as long as the 802.1Q configuration is
consistent within an EtherChannel port group.
In a service-provider network, you can use Layer 2 protocol tunneling to enhance the creation of
EtherChannels by emulating a point-to-point network topology. When protocol tunneling is enabled on
the service-provider switch for PAgP or LACP, remote customer switches receive the protocol data units
(PDUs) and can negotiate automatic creation of EtherChannels.
To enable tunneling of PAgP, LACP, and UDLD packets, you must have a point-to-point network
topology. To decrease the link-down detection time, you should also enable UDLD on the interface when
you enable tunneling of PAgP or LACP packets.
Protocol tunneling is disabled by default but can be enabled for the individual protocols on 802.1Q
tunnel ports, access ports. or trunk ports
Catalyst 3750 Metro Switch Command Reference
2-226
Modification
This command was introduced.
Support was added for the point-to-point [pagp | lacp | udld] keywords.
Support was added for LLDP tunneling.
Chapter 2 Catalyst 3750 Metro Switch Cisco IOS Commands
OL-9645-10