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Cisco 10000 Series Router Software Configuration Guide
OL-2226-23
Chapter 20 Configuring L2 Virtual Private Networks
Configuration Tasks for L2VPN
Prerequisites for IEEE 802.1Q Tunneling (QinQ) for AToM
In Cisco IOS software Release 12.2(33)SB, the QinQ (short for 802.1Q-in-802.1Q) tunneling and tag
rewrite feature is supported on the following Cisco 10000 series engines and line cards:
• PRE-2, PRE-3, and PRE-4 engines
• 8-port Fast Ethernet line card (ESR-HH-8FE-TX)
• 2-port half-height Gigabit Ethernet line card (ESR-HH-1GE)
• 1-port full-height Gigabit Ethernet line card (ESR-1GE)
• SPA line cards
Restrictions for IEEE 802.1Q Tunneling (QinQ) for AToM
In Cisco IOS Release 12.2(33)SB, the QinQ tunneling and tag rewrite feature has the following
restrictions:
• Up to a maximum of 447 outer-VLAN IDs and up to 4095 inner VLAN IDs can be supported for the
Ethernet QinQ over AToM feature.
• Only Unambiguous VLAN tagged Ethernet QinQ interfaces are supported in this release. i.e. The
Ethernet VLAN QinQ rewrite of both VLAN Tags capability is supported only on ethernet
sub-interfaces with a QinQ encapsulation and explicit pair of VLAN IDs defined.
Ethernet VLAN Q-in-Q AToM
In Metro Ethernet deployment, in which CE routers and PE routers are connected through an Ethernet
switched access network, packets that arrive at PE routers can contain up to two IEEE 802.1q VLAN
tags (one inner VLAN tag which identifies the customer; and another outer VLAN tag which denotes the
customer's service provider). This technique of allowing multiple VLAN tagging on the same Ethernet
packet and creating a stack of VLAN IDs is known as QinQ (short for 802.1Q-in-802.1Q).
Figure 20-2
shows how different edge devices can do L2 switching on the different levels of the VLAN stack.
Figure 20-2 Ethernet VLAN QinQ
When the outer VLAN tag is the service-delimiting VLAN tag, QinQ packets are processed similar to
the ones with one VLAN tag (case previously named Ethernet VLAN Q-in-Q modified, which is already
supported in the 12.2(31) SB release). However, when a customer must use a combination of the outer
and inner VLAN tags to delimit service for customers, the edge device should be able to choose a unique
pseudowire based on a combination of the inner and outer VLAN IDs on the packet shown in
Figure 20-3. The customer may want to be able to rewrite both the inner and the outer VLAN IDs on the
traffic egress side.
270305
Inner vlan
or Customer-
vlan-id
Outer vlan or
Service Provider-
vlan-id
ETH
Port
PE1
PW
MPLS
PE
VLA
Stacked
VLAN