Connecting IPv4 Islands over IPv6 MPLS Using IPv4 Provider Edge Routers (4PE)

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Last updated 2017-09-12 (latest revision 2017-03-11)
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


This document explains how to interconnect IPv4 islands over a Multiprotocol Label Switching (MPLS)-enabled IPv6-only core. This approach relies on IPv4 Provider Edge routers (4PE), which are Dual Stacks in order to connect to IPv4 islands and to the MPLS core. The 4PE routers exchange the IPv4 reachability information transparently over the core using the Multiprotocol Border Gateway Protocol (MP- BGP). MP-BGP is extended to do this. A new Subsequence Address Family Identifier (SAFI) with corresponding new format Network Layer Reachability Information (NLRI), is introduced. The BGP Next Hop field is used to convey the IPv4 address of the 4PE router, a field is added in Network Layer Reachability Information (NLRI) to convey the IPv6 address of the 4PE router, so that dynamically established IPv6-signaled MPLS Label Switched Paths (LSPs) can be used without explicit tunnel configuration.


Zhenqiang Li (

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