EoMPLS support can assume a single AS topology where the pseudowire connecting the PE routers at the
two ends of the point-to-point EoMPLS cross-connects resides in the same autonomous system; or multiple
AS topologies in which PE routers can reside on two different ASs using iBGP and eBGP peering.
The following figure illustrates MPLS over Inter-AS with a basic double AS topology with iBGP/LDP in
each AS.
Figure 8: EoMPLS over Inter-AS: Basic Double AS Topology
QinQ Mode
QinQ is an extension of 802.1Q for specifying multiple 802.1Q tags (IEEE 802.1QinQ VLAN Tag stacking).
Layer 3 VPN service termination and L2VPN service transport are enabled over QinQ sub-interfaces.
The Cisco ASR 9000 Series Routers implement the Layer 2 tunneling or Layer 3 forwarding depending on
the subinterface configuration at provider edge routers. This function only supports up to two QinQ tags on
the SPA and fixed PLIM:
• Layer 2 QinQ VLANs in L2VPN attachment circuit: QinQ L2VPN attachment circuits are configured
under the Layer 2 transport subinterfaces for point-to-point EoMPLS based cross-connects using both
virtual circuit type 4 and type 5 pseudowires and point-to-point local-switching-based cross-connects
including full interworking support of QinQ with 802.1q VLANs and port mode.
• Layer 3 QinQ VLANs: Used as a Layer 3 termination point, both VLANs are removed at the ingress
provider edge and added back at the remote provider edge as the frame is forwarded.
Layer 3 services over QinQ include:
• IPv4 unicast and multicast
• IPv6 unicast and multicast
• MPLS
• Connectionless Network Service (CLNS) for use by Intermediate System-to-Intermediate System (IS-IS)
Protocol
In QinQ mode, each CE VLAN is carried into an SP VLAN. QinQ mode should use VC type 5, but VC type
4 is also supported. On each Ethernet PE, you must configure both the inner (CE VLAN) and outer (SP
VLAN).
The following figure illustrates QinQ using VC type 4.
L2VPN and Ethernet Services Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.3.x
78
Implementing Point to Point Layer 2 Services
QinQ Mode
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