Have just switched from Netgear DG834G v3 to v4. Whilst running RouterStats I have discovered a tab in Telnet that indicates I can set my target margin. I assume that my default noise margin is the value (about 15dB) I see when I reboot the router and I understand that if I reduce the noise margin I can sync at a higher speed and ultimately get a better IP. I have a long line (atten. 52db) and an erratic noise problem which regularly reduces my margin to 2 or 3 dB. Given this scenario should I try to set a lower target margin? Any other advice on this appreciated. I have looked at some advice but it seems aimed at those who know about these things to start with which is not me.
If your force negotiation at a lower NM, then you will increase instability on the line. Given the swing in NM you are experiencing, I'd be wary of creating conditions where the router was dropping frequently, as you will likely end up with an even lower sync speed if the resync occurs when noise is present.
It will only work on adslmax and LLU connections but not on BT adsl2+ lines