Administrator Guide

Layer 2 Switching Commands 832
CE interfaces must be configured in dot1q-tunnel mode with the PVID
configured with the outer tag (native) VLAN ID for the associated service
provider (SP) interface. Configure the outer VLAN ID using the switchport
access vlan command. All MAC address learning and forwarding occurs on
the outer VLAN tag. The VLAN ID must be common to both the SP port and
the CE ports.
The service provider interface must be configured for egress tagging (trunk or
general mode) with a native VLAN identical to the PVID of the associated
CE ports. SP interfaces should be configured with a single VLAN ID. A trunk
mode port will accept untagged packets on the native VLAN and be a
member of any newly created VLANs by default. In general mode, it is
possible to directly configure the port to only accept tagged packets with a
single VLAN ID.
It is not possible to configure an inner VLAN TPID value. The inner VLAN
TPID value is always Ethernet (0x8100).
Multiple groups of associated CE and SP ports can be defined by configuring
the groups with unique VLAN IDs.
The port mirroring logic stage occurs after the after the tag processing stage
on ingress and before the tag processing stage on egress. When mirroring
packets associated with SP or CE ports, the outer VLAN tag may or may not
appear in the frame. Due to the internal processing of QinQ tagging, the
TPID of ingress frames mirrored from the SP port will always be 0x8100. In
addition, packets forwarded internally across a stacking link may have
different tags applied than packets forwarded on a local egress port. This is
due to the processing required for forwarding across a stack.
Example
This example configures ports Gi1/0/10 through Gi1/0/24 as CE ports using
VLAN 10 as the service provider VLAN ID. See the example for the
switchport dot1q ethertype command to configure an associated SP port.
console(config)#vlan 10
console(config-vlan10)#exit
console(config)#interface range gi1/0/10-24
console(config-if)#switchport access vlan 10
console(config-if)#switchport mode dot1q-tunnel
console(config-if)#exit