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Software Configuration Guide—Release 12.2(25)SG
OL-7659-03
Chapter 18 Configuring 802.1Q and Layer 2 Protocol Tunneling
Configuring 802.1Q Tunneling
• EtherChannel port groups are compatible with tunnel ports as long as the 802.1Q configuration is
consistent within an EtherChannel port group.
• Port Aggregation Protocol (PAgP), Link Aggregation Control Protocol (LACP), and UniDirectional
Link Detection (UDLD) are supported on 802.1Q tunnel ports.
• Dynamic Trunking Protocol (DTP) is not compatible with 802.1Q tunneling because you must
manually configure asymmetric links with tunnel ports and trunk ports.
• Loopback detection is supported on 802.1Q tunnel ports.
• When a port is configured as an 802.1Q tunnel port, spanning-tree bridge protocol data unit (BPDU)
filtering is automatically enabled on the interface. Cisco Discovery Protocol (CDP) is automatically
disabled on the interface.
Configuring an 802.1Q Tunneling Port
To configure a port as an 802.1Q tunnel port, perform this task:
Use the no vlan dot1q tag native global command and the no switchport mode dot1q-tunnel interface
configuration command to return the port to the default state of dynamic auto. Use the no vlan dot1q
tag native global configuration command to disable tagging of native VLAN packets.
Command Purpose
Step 1
Switch# configure terminal
Enters global configuration mode.
Step 2
Switch(config)# interface
interface-id
Enters 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 64).
Step 3
Switch(config-if)# switchport
access vlan
vlan-id
Specifies the default VLAN, which is used if the interface stops trunking.
This VLAN ID is specific to the particular customer.
Step 4
Switch(config-if)# switchport mode
dot1q-tunnel
Sets the interface as an 802.1Q tunnel port.
Step 5
Switch(config-if)# exit
Returns to global configuration mode.
Step 6
Switch(config)# vlan dot1q tag
native
(Optional) Sets the switch to enable tagging of native VLAN packets on
all 802.1Q trunk ports. When not set, and a customer VLAN ID is the
same as the native VLAN, the trunk port does not apply a metro tag, and
packets could be sent to the wrong destination.
Step 7
Switch(config)# end
Returns to privileged EXEC mode.
Step 8
Switch# show dot1q-tunnel
Displays the tunnel ports on the switch.
Step 9
Switch# show vlan dot1q tag native
Displays 802.1Q native-VLAN tagging status.
Step 10
Switch# copy running-config
startup-config
(Optional) Saves your entries in the configuration file.