The Apple Airport Extreme works well with Comcast Native IPv6. Specific application notes are included below.
Overview -
Any Apple Airport Extreme released in the last three years with firmware 7.6.1 or newer provides both IPv6 native connectivity and IPv4 NAT connectivity. Comcast Business Internet assigns a dynamic /128 address for the WAN connection and delegates a /56 prefix for LAN use. Since the Airport has one LAN, common to both Ethernet and WiFi, it uses a /64 prefix obtained from the /56 delegation. IPv6 DNS query settings are also provided to the LAN connected systems.
Configuratiion -
The IPv6 specific configuration steps below assume a standard setup for IPv4 and Comcast connections.
Using Airport Utility 6.1 or newer:
IPv6 Application Notes -