I was upgraded to VDSL on Monday (Plusnet). At first I could not get my 2850n to connect, and had to fall back to the supplied VDSL modem into port 4. But I had some significant problems with that which I was unable to overcome. Essentially my mail server was unreachable from the internet despite the fact that it worked fine when the 2850 was connected directly via ADSL. Normal internet access from all internal clients worked fine, and despite working on this for hours I could not find the cause.

So at this point I thought I would go back to plan A - get the 2850n to connect directly to the VDSL line. I had followed the instructions from the Draytek website ( http://www.draytek.co.uk/support/guides/kb-vigor-v2850-setup ), and set the VLAN tag to 101, but the 2850 would not connect - it appeared to never sync to the signal.

After much Googling I found references to the VDSL profile which BT currently use, which is 17a (corresponding to a 17MHz signal). When I went to VDSL->VDSL Setup and checked the box for 17a the 2850 then finally proceeded to connect OK. However the support document does not suggest this should be necessary - is the reality that this should be added to that document, or is this a setting that the 2850 should have picked up automatically?

i think the guide is only for BT infinity profile
It should detect the 17a profile automatic, in most cases it does ... with my 2850 all profiles are ticked by default (after a firmware update using the *rst* file), maybe you unticked in the past & updated firmware with the *all* file? the *all* file will keep the previous firmware settings

Are you saying that profile is only appropriate when your ISP is BT? If so, it would be interesting to know what profile other ISPs use. It would be a way for ISPs to sell different speeds of VDSL/FTTC connections, but I am not aware that they do this. As far as I was aware all FTTC connections use the same profile, and currently this is 17a. But I am not certain about this so would welcome any further info from anyone who does know.

Regarding the checkboxes - prior to upgrading to fibre I had not even looked at the page for VDSL Setup, and so had definitely not unchecked all the checkboxes. I guess from what you're saying the checkboxes may be provided so that you can force a modem to only use one profile when more than one is available on the connection, by only checking one checkbox. The UI is not very clear in this respect - some explanation would be very useful. It is not helped by the fact that the User Guide does not even mention the VDSL Setup screen, let alone how to use it!

Furthermore it seems that in my case at least none of the checkboxes were checked, and one at least needs to be checked in order that a connection can be established as there does not seem to be any automatic detection in place, or if there is it only looks for the checked profiles.

As far i know all providers use 17a but when i mean BT profile, i mean the current settings at draytek page, the setup is based for BT
Of course other providers has almost same settings and profiles

About the vdsl setup of the 2850, i mean all profiles are checked by default (you are correct) and the 2850 should detect the correct one .. but for a reason with plusnet did not detect automatic the 17a profile, so by unticking all the other profiles and just ticked the 17a seems it done the correct job

I always (when updating firmwares) going to adsl or vdsl settings and add them manually, instead of leaving them to auto (such MTU, multimode, authentication etc - for adsl
bit swap on, carrier A43 - when had vdsl worked and with B43) and ticked only the 17a & 30 profile (talk talk fibre)