They also advise that the target SNR for the line and can vary upon different equipment (which might explain the disparity on stats between the 2 modems

Well the missing bit seems to be "...for the line can and does vary ...". But even when corrected, the statement is simply wrong. Barring faulty equipment such as we suspect the Zyxel may be.

...as I've always connected at 6db, has the exchange been getting fooled into thinking it doesn't need to drop the target?

This seems to me quite likely, though with a roundabout sort of logic.

I would be fairly sure the Zyxel is reporting 6dB when the target figure is actually 12dB. Quite how you get the decent sync I'm not sure, but that will be down to how the software at each end negotiates.

It is relatively simple these days for ISPs to get the noise margin reset, but if you do keep the Netgear connected then you should find out in 10-14 days whether the DSLAM is going to lower the target automatically. A longer wait, but less hassle if it works.

Just to update this, tonight I checked the stats on the DNG2200 and the noise margin was down to 9db and the sync speed up to 3774. A reboot of the router gave the same stats.

The router been connected for over 12 days without a resync, so it looks like the noise margin has been lowered at the exchange. I just hope that in another 2 weeks or so the target will drop back down to 6db.

A day-time connection would give a bit more speed, but don't do several!

Today it looks like my target noise margin has been reset back down to 6db, as my router re-connected this morning with the following stats

Connection speed 4416 kbps
Line attenuation 60db
Noise margin 6.3db

This change is just over 14 days since the last step change of the noise margin, so it does look like the automatic system for dropping target noise margin does work.

Nice to know it is still working.

Your Zyxel certainly seems to have been fooling the system.

4416kbps on 60dB attenuation is really good! It was worth waiting to see what the system did I reckon.

One of the reasons I have been reluctant to replace my 2Wire BT 2700HGV (see other thread) is its ability to run at low SNRs.

It is currently showing
Down Up
Current Rate: 7392 kbs 448 kbs
Current Noise Margin: 4.0 dB 17.0 dB
Current Attenuation: 30.6 dB 16.0 dB

The BT1800 offers the same characteristics.

> Tweaking to --snr 1 is extreme. Starting from a 6dB setting (if done in the daytime)
> you would almost certainly (on BT Wholesale) cause a rise as above. Certainly a
> permanently lowered IP Profile.

... interested to see you say about permanent profile lowering. I've just started tweaking SNR because frequent power cuts make the line seem unstable to the DLM. My 6dB connect rate is 2.2 meg G.DMT due to long line length. When the SNR margin goes to 15dB I'm often down to 700kbps and the wait for it to increase seems like an eternity. Just got a DG834GT, loaded DGTeam connected @ 15dB then changed the percentage to 5% to give a daytime 6dB margin (night is about 4dB). This gave me a sync connect of 1.8 meg.

I'm a bit concerned, can you elaborate on what you mean?

I'm with BT for phone and broadband. Attempting to get a fixed SNRM out of India is like pulling teeth. Whenever you mention slow internet they suggest change wifi channel to better it