VDSL modem/router IP address?

With FTTC, does the VDSL modem/router (i.e. the device that connects to telephone line) have two IP addresses? Does FTTP work in the same way?

The router does, not the modem.

Thanks, Would an FTTP installation always used a separate fibre modem, or can you get routers with a fibre optic port?

Dunno, but for BT Infinity the same router, the Home Hub 3 is used for both FTTC and FTTP.

You can get routers with VDSL modem (fibre optic port) builtin, but pretty expensive. FritzBox is one, and a Draytek (£239 or so), and I think there are a couple of others.

They don't always behave as well as the modem Openreach supplies. VDSL standards are still 'flexible' enough that you usually get best results by using the same manufacturer for the modem as the cabinet uses; Openreach usually provide a modem to match the cabinet you are connected to.

VDSL uses copper or aluminum wires. I meant something that would connect to an optic fibre as FTTH or Gigaclear might provide.

The device you're thinking of is usually called an ONT - Optical Network Terminal. Invariably the ONT is supplied by the company from whom you rent the fibre connection - I don't think they'd be happy with people connecting up random ONTs. Not only is there a danger of fracturing the fibre by rough handling, any compatibility issues will potentially stamp on the upstream connections of the other users of that PON.

What is the problem with having a seperate FTTC modem / FTTH ONT and router? To me, it seems a better solution, not least as you don't have to junk a viable router when changing or upgrading your connection technology.

The internal fibre in the property is a short run of slightly tougher fibre, so if broken only the length between the outside wall of the home and the ONT need replacing.

In the case of Gigaclear that short length also appears to be something that the customer can install.

varies by service, but in general FTTP services come with an ONT box which presents a number of ethernet socket(s) for services. You would plug an ethernet router into one port for broadband, perhaps a VoIP device into another for a phone (or the ONT may have an analogue phone socket), TV service via a 3rd etc.