The 6PE MP-BGP routers support:
IPv4 and IPv6 dual-stack
MP-BGP to exchange IPv6 reachability information:
The 6PE routers exchange IPv6 reachability information using MP-BGP (AFI 2, SAFI 4).
An IPv4 address of the 6PE router is encoded as an IPv4-mapped IPv6 address in the BGP next-hop field. This is usually the IPv4 system address.
The 6PE router binds MPLS labels to the IPv6 prefixes it advertises. SR OS routers advertise the IPv6 explicit null (value 2) in advertised 6PE routes but accept any arbitrary label from peers.
The most preferred tunnel to the BGP next-hop allowed by the 6PE resolution filter (config>router>bgp>next-hop-resolution>labeled-routes>transport-tunnel>family label-ipv6>resolution-filter) is used to tunnel the traffic to the remote 6PE router.