Specifications

Configuring Routing Between VLANs
How to Configure Routing Between VLANS
40
DETAILED STEPS
Note If there is an explicitly defined native VLAN, VLAN1 will only be used to process CST.
Configuring IEEE 802.1Q-in-Q VLAN Tag Termination
Encapsulating IEEE 802.1Q VLAN tags within 802.1Q enables service providers to use a single VLAN
to support customers who have multiple VLANs. The IEEE 802.1Q-in-Q VLAN Tag Termination feature
on the subinterface level preserves VLAN IDs and keeps traffic in different customer VLANs segregated.
Prerequisites
You must have checked Feature Navigator to verify that your Cisco device and software image support
this feature.
You must be connected to an Ethernet device that supports double VLAN tag imposition/disposition or
switching.
Command or Action Purpose
Step 1
enable
Example:
Router> enable
Enables privileged EXEC mode.
• Enter your password if prompted.
Step 2
configure terminal
Example:
Router# configure terminal
Enters global configuration mode.
Step 3
interface fastethernet
slot/port.subinterface-number
Example:
Router(config)# interface fastethernet 4/1.100
Selects a particular interface to configure.
Step 4
encapsulation dot1q vlanid native
Example:
Router(config-subif)# encapsulation dot1q 20
native
Defines the encapsulation format at IEEE.802.1Q (dot1q)
and specifies the VLAN identifier. VLAN 20 is specified as
the native VLAN.
Note If there is no explicitly defined native VLAN, the
default VLAN1 becomes the native VLAN.
Step 5
bridge-group bridge-group
Example:
Router(config-subif)# bridge-group 1
Assigns the bridge group to the interface.