Airport Time Capsule Not Connecting to Internet

Manual firmware downgrade... I will post this separately so as to not confuse you.

It is actually possible to grab the firmware.. and download it to your computer.. and then upgrade anytime. Even in full network isolation.

Cannot Update 802.11ac BIOS

I am not sure all our posts on doing this have survived.. this one is 7.7.3 but is still ok and will work. Once you download and install you can upgrade later to one of the newer ones.

Here is the exact method for doing 7.7.7

1. Download the firmware. (Note this link is ONLY for the Time Capsule AC model)

http://apsu.apple.com/data/119/031-45984-20160525-920F19D6-2138-11E6-BEF6-3D5355 29DBDF/7.7.7.basebinary

2. In airport utility.. click the icon of your TC.. option-click the current firmware number.. select other.

3. Select the firmware from downloads.

4. Continue to the firmware update.

5. Status

6. Updating.. update up or down.. still update.

7. Voila.. TC gen5 (id 119) now operating on 7.7.7

Plus an annoying reminder to update and a red error circle.

Well stick with that for the time being.. if it falls over.. then setup the TC with static IP.. in your case..

That means anytime your computer loses connection to the TC.. you can always force the connection to the known IP address..

Part2 Optional

You can also do an extra mod..

If your TC keeps getting lost.. this can help.

Change the TC to a router again but no NAT.

So you set the Network Router mode to DHCP only.. which also means the WAN of the TC must be the connector to the upstream.. ie BT router.

Now actually getting values to stick here is kind of hard.. I spent quite a while as it would say either beginning of the range was wrong or end of the range was wrong.. that is just one of those strange things Apple routers do.. I know exactly what all the other devices are set to .. so it has no need whatsoever to do this.. Anyway if your first values don't work.. no problem.. keep cycling the numbers.. I ended up 20 to 88 .. In your case it might be 10 or 11.. and then top number.. 51 .. whatever it is no biggie.. swap to DHCP and NAT and then swap back if it gets bound up.

I would also change via Network Options to 1hr lease time.

Any clients of the TC then pick up address from the TC and all the correct things happen.. bonjour stays active.. Apple clients are very happy connected to Apple router.. instead of bridged AP.

And there is no double NAT problem.. for me it is significantly more reliable than using bridge.

After owning my Airport Extreme for about 3 years

Just to start by confirming you own one only airport.. a Time Capsule NOT an Extreme which are two different products.

Also at about 3 years it is the Tall AC version?? Not the flat older series.

I will press on regardless assuming a single TC AC version.

The new firmware.. is causing some issues.. imho those issues are not the firmware itself.. but the disturbance in the FORCE (ie status quo or working router) .. which on older devices does seem to cause problems.

You can attempt to go back to 7.7.7 as a first step to fixing it.. factory reset and then see if the problems stop or keep going..

There is next to no problem in downgrading because the security issues fixed are actually only in Extend wireless setup or client issue not the Airport itself.

In bridge I would also swap the cable that I guess currently goes WAN TC to LAN ISP modem router.. to LAN TC to LAN ISP modem router.. in bridge you can use either but WAN seems to die or misbehave more often.

There are more complicated fixes so try the easy ones and report.

Ok.. lets go for the big kahuna.. !!

Setup the TC again.. this time do it statically and with manual setup..

I need to know your ISP modem router.. make and model??

Is your ISP using IPv6? (This is not a major concern because the router side is likely still IPv4 but do tell me if you are actually using IPv6)

What is the IP address of the ISP modem router.. and please do log into it and tell me also the DHCP range.. ??

While you are there can you please cut down the DHCP range to say 2-100 or 101-250 .. something simple and easy to remember. If you find that is difficult. Ignore it.. we can live without.. just tell me the IP.. generally 192.168.1.1 (something like that).

I did go into my BT Smarthub and for some reason it had the TC showing as static and not DHCP

Not sure.. but the TC should be DHCP but not all routers behave the same..

If you still have trouble do give me a screenshot of the TC setup and perhaps show me how the BT smarthub is showing the TC as well.. we might need to make sure the Smarthub does correctly fix the TC address.. if it has DHCP reservation.. you can reserve the TC address and this will help it keep ARP table updated.