Somebody please help - I am going depsair with this problem.
We have a Cisco 1841 router on BT ADSL 2 broadband. Roughly around every 3 weeks, the broadband will drop off and will not reconnect for extremely lengthy periods of time (up to 2 days).
After running 'sh dsl int atm 0' on the IOS, I see that the Noise Margin is fluctuating enormously. However, it does spend most of its time between -1.5 and +1.5. When it does jump to +12 the connection establishes and we have broadband, for about 15 seconds. At this point, the Noise Margin must drop down again and the router loses connection.
The IOS logging shows: 'Interface ATM0, changed State to Down' and 'Interface ATM0, changed State to Up', which reflects the interface going down when the Noise Margin drops to low, and then connecting when it increases.
Is there any way to get the cisco router to adapt to the extremely low Noise Margin? The most frustrating thing about this is that buying and installing a cheap Netgear or Belkin router, which are great at holding connections at low or even negative noise margins, works no problems and is quite stable - bit of a kick in the teeth!
I don't envisage BT being of much help here, as they are difficult to deal with atthe best of times.
Hope someone can help.