Configuring Layer 2 Tunneling - Cisco Catalyst 3750 Software Configuration Manual

Configuring Layer 2 Protocol Tunneling
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Configuring Layer 2 Tunneling

Beginning in privileged EXEC mode, follow these steps to configure a port for Layer 2 protocol
tunneling:
Command
Step 1
configure terminal
Step 2 interface interface-id
Step 3 switchport mode access
or
switchport mode dot1q-tunnel
or
switchport mode trunk
Step 4 l2protocol-tunnel [cdp | stp | vtp]
Step 5 l2protocol-tunnel
shutdown-threshold [cdp | stp | vtp]
value
Catalyst 3750 Metro Switch Software Configuration Guide
13-14
If an encapsulated PDU (with the proprietary destination MAC address) is received from a tunnel
port or access or trunk port with Layer 2 tunneling enabled, the port is shut down to prevent loops.
The port also shuts down when a configured shutdown threshold for the protocol is reached. You can
manually re-enable the port (by entering a shutdown and no shutdown command sequence) or if
errdisable recovery is enabled, the operation is retried after a specified time interval.
Only decapsulated PDUs are forwarded to the customer network. The spanning-tree instance
running on the service-provider network does not forward BPDUs to tunnel ports. No CDP packets
are forwarded from tunnel ports.
When protocol tunneling is enabled on an interface, you can set a per-protocol, per-port, shutdown
threshold for the PDUs generated by the customer network. If the limit is exceeded, the port shuts
down. You can also rate-limit BPDUs by using QoS ACLs and policy maps on a tunnel port.
When protocol tunneling is enabled on an interface, you can set a per-protocol, per-port, drop
threshold for the PDUs generated by the customer network. If the limit is exceeded, the port drops
PDUs until the rate at which the port receives them is below the drop threshold.
Because tunneled PDUs (especially STP BPDUs) must be delivered to all remote sites for the
customer virtual network to operate properly, you can give PDUs higher priority within the
service-provider network than data packets received from the same tunnel port. By default, the
PDUs use the same CoS value as data packets.
Purpose
Enter global configuration mode.
Enter the interface configuration mode and the interface to be configured as
a tunnel port. This should be the edge port in the service-provider network
that connects to the customer switch. Valid interfaces include physical
interfaces and port-channel logical interfaces (port channels 1 to 12).
Configure the interface as an access port, an 802.1Q tunnel port or a trunk
port.
Enable protocol tunneling for the desired protocol. If no keyword is entered,
tunneling is enabled for all three Layer 2 protocols.
(Optional) Configure the threshold in packets per second to be received for
encapsulation before the interface shuts down. The port is disabled if the
configured threshold is exceeded. If no protocol option is specified, the
threshold is applied to each of the tunneled Layer 2 protocol types. The
range is 1 to 4096. The default is to have no threshold configured.
Note
Chapter 13 Configuring IEEE 802.1Q and Layer 2 Protocol Tunneling
If you also set a drop threshold on this interface, the
shutdown-threshold value must be greater than or equal to the
drop-threshold value.
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