Guest mode isn't available with some IPv6 configurations on AirPort devices
To use Guest mode and IPv6 at the same time, you might need to add a value to the delegated prefix setting on your AirPort Extreme, AirPort Express, or AirPort Time Capsule.
Depending on how your IPv6 configuration is set, Guest network mode might not be available on your AirPort device:
When you specify a LAN prefix length for Manual Router or Tunnel mode that's equal to 64 bits, there are insufficient bits available to allow for a guest network. In these cases, IPv6 Guest network is unavailable.
If a prefix delegation isn't provided, your AirPort device assumes a prefix of 64. This also disables guest networking for IPv6.
You can use AirPort Utility to set an IPv6 prefix of 48 on your AirPort device. This allows you to use both IPv6 and Guest network mode at the same time.
Ask your network provider for your IPv6 settings.
Open AirPort Utility, then select the AirPort device you’re setting up. Enter the device password if prompted.
Click or tap Internet, then choose Internet Options.
From Configure IPv6, choose Manually.
From IPv6 Mode, choose Native or Tunnel per your network provider's instructions.
Enter the IPv6 WAN Address, Default Route, and other information you received from your network provider.
Enter a /48 address in the IPv6 Delegated Prefix field. Click Save, then click Update to update your AirPort device.
