The 6PE MP-BGP routers support:
IPv4/IPv6 dual-stack
MP-BGP can be used between 6PE routers to exchange IPv6 reachability information as follows:
The 6PE routers exchange IPv6 prefixes over MP-BGP sessions running over IPv4 transport. The MP-BGP AFI used is IPv6 (value 2).
An IPv4 address of the 6PE router is encoded as an IPv4-mapped IPv6 address in the BGP next-hop field of the IPv6 NLRI. By default, the IPv4 address that is used for peering is used. It is configurable through the route policies.
The 6PE router binds MPLS labels to the IPv6 prefixes it advertises. The SAFI used in MP-BGP is the SAFI (value 4) label. The router uses the IPv6 explicit null (value 2) label for all the IPv6 prefixes that it advertises and can accept an arbitrary label from its peers.
LDP is used to create the MPLS full mesh between the 6PE routers and the IPv4 addresses that are embedded in the next-hop field are reachable by LDP LSPs. The ingress 6PE router uses the LDP LSPs to reach remote 6PE routers.