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The router maintains statistics on the line quality. Using the CLI, type:

adsl show perf

You will get two sets of figures, one for the downstream data path (from the ISP to you) and one for the upstream data path (from you to the ISP). There are three different figures to look at.

First, noise margin
This is a measure of how good your data signal is relative to the noise on the line. This should be a high number and in any case no lower than around 6 dB. If it's this low you could find the router gets link errors or even sync problems.

The second is attenuation
Measures how much signal loss there is on the line - this should be a low figure and in any case should be no more than around 60-65 dB.

The third is output power
Indicates how hard the router is working to maintain the link. High numbers (around 19 or above) can indicate possible problems.

Any of these numbers near or at the limits described can cause the router to lose sync or have high error rates resulting in poor internet performance and are usually due to poor cabling, interference or a line which is at the distance limit of where ISP can still provide ADSL from the local exchange.

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by IKARI See Profile
last modified: 2004-10-12 23:55:27