Configuring Layer 2 Tunneling - Cisco Catalyst 4500 Series Software Configuration Manual

Chapter 30 Configuring 802.1Q Tunneling, VLAN Mapping, and Layer 2 Protocol Tunneling
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Note

Configuring Layer 2 Tunneling

To configure a port for Layer 2 protocol tunneling, perform this task:
Command
Step 1
Switch# configure terminal
Step 2
Switch(config)# interface
interface-id
Step 3
Switch(config-if)# switchport
mode access
or
Switch(config-if)# switchport
mode dot1q-tunnel
or
Switch(config-if)# switchport
mode trunk
Step 4
Switch(config-if)#
l2protocol-tunnel
point-to-point
EtherChannel port groups are compatible with tunnel ports when the 802.1Q configuration is
consistent within an EtherChannel port group.
If an encapsulated PDU (with the proprietary destination MAC address) is received on a 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 reenable the port (by entering a shutdown and a no shutdown command sequence). 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 Layer 2 protocol tunneling
ports. CDP packets are not forwarded from Layer 2 protocol tunneling 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 limit the BPDU rate by using QoS ACLs and policy maps on a Layer 2 protocol
tunneling 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 it receives them is below the drop threshold.
Because tunneled PDUs (especially STP BPDUs) must be delivered to all remote sites so that the
customer virtual network operates 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.
If Layer 2 protocol tunneling is not configured on a system, Layer 2 protocol tunneling packets
are handled as data packets and this situation does not apply.
Purpose
Enters global configuration mode.
Enters interface configuration mode, and enter 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 can
be physical interfaces and port-channel logical interfaces (port channels 1
to 64).
Configures the interface as an access port, an 802.1Q tunnel port or a trunk
port.
Enables protocol tunneling for the desired protocol. If no keyword is
[ |
cdp
entered, tunneling is enabled for all three Layer 2 protocols.
| | | ]
stp stp vtp
Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
Configuring Layer 2 Protocol Tunneling
30-17