SFR France is using Cisco’s L2TP Softwire Tunnel technology to leverage its existing investment in IPv4 network access infrastructure to quickly provide IPv6 services to residential customers. The carrier has selected Cisco Carrier-Grade Internet Protocol Version 6 (CGv6) Solution as a first step in the transition of their network infrastructure to IPv6. 
Cisco said its IPv6 over L2TP approach requires limited investment and impact on existing infrastructure. Dual-stack IPv4/IPv6 services on the Residential Gateway (customer) side are enabled. The solution allows IPv6 sites to communicate with each other over an IPv4 core.
An open standard for L2TP is defined in RFC 5571, which describers IPv6 global connectivity over an IPv4 core. This document was approved in August 2009 by the Internet Engineering Steering Group to be published as a Standards Track RFC.
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