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What is the behavior of a virtual tunnel interface in different services routing instances?
If you configure a virtual tunnel (vt) interface on the egress PE router and that router is also a transit router for the point-to-multipoint LSP, the penultimate hop router sends just one copy of each packet over the link to the egress PE router. A vt interface can perform two lookups on an incoming packet, one for the multicast MPLS lookup and one for the IP lookup. This applies to Layer 3 VPNs and VPLS point-to-multipoint LSPs.
This is the behavior of vt-interface in different services:
For more information, click Layer 2 VPNs and VPLS Feature Guide.