Unless you are currently using IPv6, be sure that your AirPort Extreme is configured to use the “Link-local only” setting for IPv6.
You can set this using the AirPort Utility:
AirPort Utility > Select the Extreme > Edit
Internet > Internet Options > Configure IPv6: Link-local only
On your Mac:
System Preferences > Network > Wi-Fi > Advanced
TCP/IP > Configure IPv6: Link-local only