In reply to a post by Ignitionnet:

As I recall BT Wholesale mandate CHAP. No idea what Vodafone use. In theory as they aren't using a wholesale provider, but are one themselves they have no need to use anything.

Vodafone do their best to stop their VDSL customers using their own equipment by refusing to tell them their connection userid and passwords. So if their combined router modem can be configured to work with a separate modem their is a chance that the details could be obtained by sniffing the router-modem connection. But they may well be encrypted