I have just purchased a 2750Vn. I have read and actioned the instructions on the DrayTek web site re connecting to BT infinity. I get a connection OK but it only lasts for about 3 minutes before going down and then coming up again with a new dynamically assiged IP address from BT.
The BT modem/homehub works without a problem. Any ideas ?
thanks

I moved the vigor and made a direct connection from 1 PC and looked through all the settings without connecting the vigor to the phone socket. I did not make any changes as I did not see anything relevant to change. Then I plugged in the vigor into the phone socket and up came the infinity broadband OK. In fact very ok as the connection lasted a fair while (20 mins) so I though I would again connect it to my Ethernet switchbox. When I unplugged the PC to put it back in the switchbox and then put another cable from the vigor to the switchbox this again caused the fibre broadband to loose its connection to go down. (strange as I had not unplugged the vigor from the phone socket connection). But the infinity broadband came up again (yet again another IP address), and this time, as I write, its been up for a whopping 49 minutes.

I will have to see how long it lasts, but its all very strange. Does anyone else experience this sort of flaky shenanigans the vigor modem ?

Oh b***er, it lasted about 1 hour 10 minutes before going down and up again.

Have you entered 101 in the WAN VLAN ID box ?

My 2750 has been connected 27d 17:00:38 according to VDSL status. Router up time 29d 01:01:24.

see: http://www.draytek.co.uk/support/kb/kb_vigor_v2750_setup.html

Thanks to those who replied. Indeed I did enter 101. The instructions on the DrayTek support page were followed in full. The router is no good at my premises for whatever reason.