Some “hidden” Cisco commands for changing/adjusting the SNR from within the Cisco. I have used this many times as Cisco Routers are much more sensitive to change and issues than any other equipment.

Go into global configuration mode and type the following:
service internal
int atm 0
dsl noise-margin (a value between -3 and 3)

The dsl noise-margin forces the router to training at a higher noise margin (sacrificing speed for stability). Setting this to 3 for example should see you get a higher noise margin, slower speed (and depending on firmware) a higher attenuation.

See  my other article about the 4.0.18 ADSL firmware as this fix combined with the latest firmware has resolved many of my Cisco 877 connection Nightmares (especially on a BT Internet connection)

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