Yeah, the Vigor 2800 has the maxdnrate command. But, this is what it says - it is the maximum sync speed that the router will attempt to sync at, not the minimum. From what I understand of the OP, they want a router where you can set the minimum, and if it doesn't manage that, it just refuses to sync. On top of that, I think maxdnrate only works for plain ADSL max lines (ADSL1), not ADSL2(+).

My only suggestion is to try and find a router which allows you set the target SNR of the sync, as if this is high enough (and interleaving is also on), that will probably stop the re-syncs happening. I know SpeedTouch modems on an older (v6) firmware allow that, but I'm sure there is newer kit available now - maybe someone can advise on that.

Sounds good at first, but to stop the resyncs happening the settings would have to make the normal sync equal to, or even lower than, the worst sync he gets when this happens. Which rather defeats the object.

As he said, loss of connection for a short period doesn't bother him. It's the fact a low sync occurs and screws the IP Profile.

I am the OP on this thread and I'm back to close out the problem in case I can help anyone that gets in here from Google.

Since I posted this the intermittent disconnects and line noise were getting progressively worse. The noise was only evident when the ADSL connection was active. A BT engineer was called out.

He attached a Hawk scope to the line and a blip showed up where the outside line from the pole meets the house. He changed that connection for new and bingo everything is fixed and I have a perfect line.

He logged it as an "HR dis" high resistance fault and said that as a voice engineer his normal tests would not have caught it, but he ran additional tests that a broadband engineer would do and it showed up.

Cheers!
Andy