Redistribution of IPv4 Routes with IPv6 Next Hop (RFC 5549)

In a network that predominantly transports IPv6 traffic, there is a need to route IPv4 routes when required. For example, an ISP that has an IPv6-only network, but has customers who still route IPv4 traffic. In this case, it is necessary to cater to such customers and forward IPv4 traffic over an IPv6 network. As described in RFC 5549, IPv4 traffic is tunneled from CPE devices to IPv4-over-IPv6 gateways. These gateways are announced to the CPE devices through anycast addresses. The gateway devices then create dynamic IPv4-over-IPv6 tunnels to remote CPE devices and advertise IPv4 aggregate routes to steer traffic. Route reflectors with programmable interfaces inject the tunnel information into the network. The route reflectors are connected through IBGP to gateway routers, which advertise the IPv4 addresses of host routes with IPv6 addresses as the next hop.