I recently changed ISPs to a cheaper plan (not by much) which provides more quota (about 40gb) per month than what I was getting from my previous provider. Along with this, I went to the 8Mb DSL plan where as previously I was on the 1.5Mb. When you start getting higher speeds, alot of other factors come into how stable your connection is.  Before I made any changes, my atm0/0/0 interface was looking like:

Speed (kbps): 7300
Noise Margin: 6.0 dB

A noise margin of 6.0 dB turns out to be the bare minimum you would want to have as it’s the borderline for a stable connection and the connection from hell. As I have been having connection issues lately, I decided to do some googling. On a few sites I came across some undocumented cisco commands, one of which was “service internal”. Normally on an ATM interface you will see something like:

adsl-gw(config)#int atm0/0/0
adsl-gw(config-if)#dsl ?
enable-training-log enable the fw training log for Showtime and failure cases
lom Loss Of Margin watch counter for line retrain
operating-mode auto or specific ADSL mode

After going into config mode:
adsl-gw(config)#service internal
adsl-gw(config)#int atm0/0/0
adsl-gw(config-if)#dsl ?
enable-training-log enable the fw training log for Showtime and failure cases
gain-setting ADSL programmable gain setting
lom Loss Of Margin watch counter for line retrain
max-tone-bits set maximum bits per tone limit
noise-margin set noise margin offset
operating-mode auto or specific ADSL mode
power-cutback Noise Threshold for Power CutBack

Voila. The setting I wanted to play with was the noise-margin. After setting the noise margin with “dsl noise-margin 2″ (settings between -3 and 3 accepted, the higher (3) the better) my DSL stats now say:

Noise Margin: 7.5 dB
Speed (kbps): 6592

The noise-margin seems to go between 7.5 and 9 which is optimal. The other setting I can try is increasing the noise-margin to 3, however I will sync at around 6200 once that’s done.

More undocumented Cisco commands here, here and here.