Inter-As Mode - Cisco CRS Configuration Manual

Ethernet over MPLS
As illustrated in the following figure, the Ethernet PE associates an internal VLAN-tag to the Ethernet port
for switching the traffic internally from the ingress port to the pseudowire; however, before moving traffic
into the pseudowire, it removes the internal VLAN tag.
Figure 4: VLAN Mode Packet Flow
At the egress VLAN PE, the PE associates a VLAN tag to the frames coming off of the pseudowire and after
switching the traffic internally, it sends out the traffic on an Ethernet trunk port.
Because the port is in trunk mode, the VLAN PE doesn't remove the VLAN tag and forwards the frames
Note
through the port with the added tag.
L2VPN forwarding using GRE tunnels is supported in the VLAN mode.
Note

Inter-AS Mode

Inter-AS is a peer-to-peer type model that allows extension of VPNs through multiple provider or multi-domain
networks. This lets service providers peer up with one another to offer end-to-end VPN connectivity over
extended geographical locations.
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.
Cisco IOS XR Virtual Private Network Configuration Guide for the Cisco CRS Router, Release 6.1.x
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Implementing Point to Point Layer 2 services