Thank you very much for your response - much appreciated. I think you confirmed my suspicions about the modem codes. I agree that the router seems to choose the default modem code for each line type, unless the user intervenes and, instead of the default option, chooses a different one.

I've tested quite a few firmware types with modem codes on my line - which seems to be affected by interreference at certain times, too (my 12:57am disconnect is almost always there) - and to confirm what you're saying, both modem codes within any firmware can be used, depending on the line type. This would then contradict the information contained in the file published by Draytek that I quoted above - unless, as you say, there are 24 in total!

What is also of interest to me is the difference between the firmware upgrade and modem code upgrade in the System Maintenance option. Do you know what the latter does and whether there are special modem code files for it? Or is it that the router 'extracts' the modem code from firmware and so you can choose between any four at a time? In the manual, it says, 'This function is used to upgrade modem code if you find built-in modem code is not suitable for Vigor router.' Again, very cryptic.

If anyone is interested to know MDM2 firmware is the one that doesn't support vectoring or G.IMP on VDSL lines (Draytek Support wrongly claimed it was the STD one). From my observations and testing, some modem codes result in more CRC errors than others, and on top of everything, when I use 'the other' VDLS modem code on the MDM2 firmware, the values for downstream and upstream (actual PSD and attenuation) are reversed. According to Draytek Support, this is meant to be like that, but I'm still unclear why, though.

As a final comment, I'll say that I've used Drayteks for a number of years now (2820n, 2830n plus and now 2762). What I've noticed is that standards are now slipping a bit: there's more focus on getting new models out (2762 vs. 2765) to keep up with competition, but at the cost of quality, not just in terms of minor issues (it's enough to have a look at the layout of some information on pages in the router's menus, and there's also the issue of less information being available than before in terms of firmware), but also in terms of how much support know and how soon, and if at all, they respond to one's queries.

Thank you very much for clarifying!

edinburgh wrote:
What is also of interest to me is the difference between the firmware upgrade and modem code upgrade in the System Maintenance option. Do you know what the latter does and whether there are special modem code files for it?

Somewhere on the Web, there is a discussion of the layout of a Draytek firmware file (i.e. .RST/.ALL etc) and the component parts that make it up. From what I recall, one of these is the "Modem Code", so I'm guessing that Draytek could, if they needed to, distribute that portion separately to the rest of the firmware.

I'm not aware that they've ever done that (but since I've spent most of the last 20 years on NTL/Virgin , it's not a topic I've followed very closely). If they do indeed have this facility, you'd think they'd use it ... one main firmware file and separate plug-in Modem Code would seem simpler to me.