In reply to Fred Baker.

Hi,

On the IPv6-only SSID there was IPv6 traffic end to end if possible. There was no NAT for the IPv6 or IPv4 ranges. Both IPv6-only and dual-stack networks used public IPv6 and IPv4 address ranges.

If an IPv6-only client wanted to communicate with an IPv4 only server then the DNS server, using DNS64, would synthesise an IPv6 address with the 'well known' IPv6 prefix. When that IPv6 client would then send traffic towards this synthetic address the ASR1006 would NAT this traffic using NAT64 into an IPv4 (from the pool on the router) to IPv4 (extracted from the synthesised address).

During FOSDEM we translated 6,711,290 connections composed out of 374,671,589 IPv6 -> IPv4 packets and 587,005,529 IPv4 -> IPv6 reply packets using NAT64. For reference there were 1,255,170,975 outgoing IPv6 packets in total. So about 30% of IPv6 traffic was towards IPv4-only servers and needed to get translated using NAT64.

There was no setup to allow IPv4 devices to talk to IPv6 clients. All our servers are dual-stacked.