Alcatel-Lucent 7450 Configuration Manual page 50

Internet Protocol Versions
6PE Control Plane Support
The 6PE MP-BGP routers support:
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6PE Data Plane Support
The ingress 6PE router can push two MPLS labels to send the packets to the egress 6PE router. The
top label is an LDP label used to reach the egress 6PE router. The bottom label is advertised in MP-
BGP by the remote 6PE router. Typically, the IPv6 explicit null (value 2) label is used but an
arbitrary value can be used when the remote 6PE router is from a vendor other than Alcatel-
Lucent.
The egress 6PE router pops the top LDP tunnel label. It sees the IPv6 explicit null label, which
indicates an IPv6 packet is encapsulated. It also pops the IPv6 explicit null label and performs an
IPv6 route lookup to find out the next hop for the IPv6 packet.
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IPv4/IPv6 dual-stack
MP-BGP can be used between 6PE routers to exchange IPv6 reachability information.
→ 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.
7450 ESS Router Configuration Guide