IPv6 Airport Proper Configuration w/ Comcast Gateway

Unfortunately right now I don't have the USB-C to Ethernet adapter for my Mac; however, I do get 10/10 with my Mac WiFi connected to the bridged/Link-Local Airport Access Point - so would that conclude that Comcast supports IPv6 fully?

Correct. This also confirms that the AirPort is not interfering with IPv6 in any way.

Also of note, if I configure the Airports as Native, but with "Share IPv6 Connection" = OFF, I get the very same result 10/10

So do I, but I notice that the AirPorts can sometimes disappear in AirPort Utility with this type of setup. Or, if they appear, there will be no green status light next to the AirPort. The light is not on at all. Restarting the AirPort might bring it back, but the same errors occur after a time. It might be a day or two, or even a week or two.

In the configuration (different than mine) you mentioned previously, where/if a user wants the Airport to instead be configured as the "main" DHCP/NAT device and selects "Native" (i.e, to hand out IPv6 addresses), wouldn't they also (at the same time) have to select "Share IPv6 Connection" to get the IPv6 addressed to be generated?

Yes, as I noted above in my example of an AirPort set up as the "main" DHCP and NAT router.

Would you ever configure Native but Share OFF?

I wouldn't, unless there were another router on the network that you wanted to use to only hand out IPv6 addresses separate from the router handing out IPv4 addresses. This is likely going to create some conflicts sooner or later though.

Is it safe to say that whatever the error (timing whatever) its NOT due IPv6 or the fact that I am using bridged Airports?

If you have the AirPorts in Link Local Only, they are not affecting IPv6 from the gateway in any way.

Oh I wanted show why I initially was confused on the Link Local function - if you read the Apple User Guide below - you can see the confusion.

Best to ignore the info from Apple since you have proven to yourself that it is not accurate. If it were, the AirPort would not be passing IPv6 info from the gateway through to connected devices. What Apple should have said....but did not.....would be to use the Link Local Only setting when there is another router on the network handling the IPv6 info from your provider.

If for some reason, you did not want the gateway to handle your Internet connection and main routing functions, and you replaced it with a simple modem only.......the kind that has only one Ethernet port......then.....you would configure the AirPort that is connected to the modem as the DHCP and NAT router with IPv6 settings. What I can't tell you is whether you would use "Native" or "Tunnel" with the service from Comcast. You would have to ask them about this, or spend some time experimenting to see if there were any differences when you were running the IPv6 checks.

All the other AirPorts would remain in Bridge Mode and Link Local Only in this type of setup.

Anyway, I have Comcast internet with an Arris SVG2482AC Gateway (I believe Comcast has full IPv6 capability

To find out whether the Comcast gateway has full IPv6 capability, you will need to temporarily power off all the AirPorts and then connect your Mac using an Ethernet cable to the Comcast gateway and then run a check like......testipv6.com

What are your results? If you see 10 out of 10, then your Comcast gateway has full IPv6 capability.

No matter what the results might be though.......the correct setting for all of the AirPorts for IPv6 is Link Local Only.

I believe that essentially prevents any Access Point (wifi) eqmt from using/seeing IPv6.

This is not correct. My AirPorts are in Bridge Mode and Link Local Only......just like yours......and I get a 10 out of 10 reading when I run the check above, indicating that all systems are go with IPv6.

Apple should have tied Bridge Mode and Link Local Only together, but they unfortunately did not. In other words, when you set up an AirPort in Bridge Mode, the setting for IPv6 should also automatically change to Link Local Only, but it does not, so you have to make this change manually.

Should these be setup as Automatic/Native?

No, not on any of the AirPorts.

Should I Enable IPv6 Sharing

No, not on any of the AirPorts.

why not?

Because the Comcast gateway is already handling IPv6 Sharing (and IPv4 Sharing as well).

Think of it this way. When the AirPorts are in Bridge Mode, all of the network IP addresses....both IPv4 and IPv6.....are handled and distributed by the gateway. The AirPorts simply pass this information through to devices that might be connected to the Wi-Fi provided by the AirPorts.

You don't want the AirPorts trying to handle IPv6 for the same reason that you don't want them trying to handle IPv4. The gateway is handling the service for both IPv4 and IPv6, and the AirPorts are passing through that information to connected devices.

Or in other words, the AirPorts are not handing out network IP addresses at all......the gateway is doing this.

This would not apply to your setup, but things would be different if you had an AirPort set up as the "main" DHCP and NAT router on the network. In that case, you would use either IPv6 Native or Tunnel, depending on your service provider and IPv6 Connection Sharing would be enabled.

If you had other AirPorts on the network set up in Bridge Mode, those AirPorts would be set up as Link Local Only with no Connection Sharing.

Recently I had an iPhone App (a sprinkler system controller) that requires some detailed communication (for a flow calibration feature) between local irrigation controllers, uploads to system servers, and back down to the cell phone app for display. This feature has been failing to display the proper data on my WiFi connected phone/app and the company tells me that they believe my network is at fault (not their Software - and ran out of ideas).

If everything else is working correctly, and this is the only App that is having problems, then I think you already know where the problem really exists.

Kind of like the mom who is watching the high school marching band noting that her son was the only one in step with the music.