I've recently put my 3Tb current-gen Time Capsule and Airport Express back into use with a new Netgear DM200 VDSL modem.
The configurations is as follows:
MODEM <-- Ethernet (30cm) --> TC <----- Ethernet (15m) ------> AEX
The Airport Express is there to provide wi-fi access to a room that get a ver poor wi-fi signal.
The TC is in bridge mode as is the AEX, configured via Airport Utility to extend the WiFi from the TC.
However, all wireless clients intermittently (about 50% of the time) get the problem of being connected to WiFi but not getting any internet access. In fact, the 'WiFi' settings screen of a connected Apple device explicitly states 'No Internet'.
This can be fixed by either switching Wi-Fi off and on or by switching to/from the 5Ghz network.
I've tried not having guest network, not having the 5Ghz network, disconnecting the AEX or switching the AEX and the TC, in case it's the TC's Wi-Fi that's the problem. Nothing seems to work.
It's as though on occasion the 'bridge' between the WiFi and the modem is not working. although some wireless clients might be working whilst others aren't.
The problem appears to only manifest itself or clear upon joining the WiFi network - if it's working, it stays working.
Wired connections are fine.
Edit - should I be using the modem in 'modem only' mode? I haven't changed any of its settings other than to enter my ISPs username and password so I assume it's in modem+router mode. If I do this then I need to configure the TC with the ISP username and password and to do DHCP etc?