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Beginner

C877 with ADSL Max keeps experiencing retrains

Hi, I have customer who has recently installed a Cisco 877 on an ADSL MAX BT circuit. The problem is that they keep getting retrains every few hours. I believe that the router is training up at too high a speed and line errors or other line issues are resulting in retrains.

I believe that forcing the sync speed down will clear the problem but there doesn?t seam to be a ?dsl line-rate? option for ADSL routers.

Does anyone know how you can force the rate at which an ADSL circuit trains to? Or alternatively change the training parameters on the router so that it doesn?t have to keep retraining?

Thanks,

Chris

9 REPLIES 9
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Frequent Contributor

Try adding an ADSL filter. After adding an ADSL filter the ADSL retrains stopped. A filter are indeed needed when a phone and an ADSL router share the same line.

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Beginner

I too am looking for a command to set a limit. At the moment my 877 connects with a very low noise margin and will intermittently drop the line.

If I could set a maximum download speed I would be able to achieve a reliable connection.

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Hi All!

I'm also having some grief with an 877 (in the UK)... the most progress I've made so far is to go to this URL :

ftp://ftp.cisco.com/pub/access/800

Download the 3.0.10 ADSL firmware. Copy it to flash, and rename to this name exactly:

adsl_alc_20190.bin

This got mine trained up fine - prior to this it appeared to be dead...

Regards

Aaron

Please rate helpful posts...

Aaron Please remember to rate helpful posts to identify useful responses, and mark 'Answered' if appropriate!
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What IOS version are you using?

I'm using 12.4(11)XJ3 in the UK without any issues. That IOS has ADSL firmware 3.0.14 embedded.

Regards

Colin

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Beginner

On my old 837 you could issue

dsl noise-margin 3

which would cause a lower sync speed to be negotiated.

Unfortunately, I too upgraded to an 877 and the above command is no longer available which makes the 877 a much less reliable unit than the 837 it replaced.

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Hi,

I guess the reasoning is that no configuration should be necessary to attain the best link (in terms of stability and speed), then again if cisco has managed to achieve this only with the latest firmware, it's a matter of spreading the information and making the fix available (thing that is already).

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I think the problem is; how do you define the "best link"? For some users a 7Mbs link that drops every 8 hours is prefered over a 6Mbs link that drops every 10 days.

However I'm the converse I'd prefer stability over speed but I have no way of configuring the new cisco to give me that.

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I understand the point you are making.

What you want, is the ability for an ADSL user (or CPE) to cap the download speed.

Apparently that was possible in some way with different ADSL chipsets of firmware. I personally think the method used (tinkering with the noise margins) was obscure and not-standard.

But, in reality it should be the ISP to cap down the speed when measurements shows that high speeds are not reliable. The ADSL firmware should continuously try to adapt the line speed to the actual line conditions if these prove to be varying during the day. But, if there is too much of a variation, a retrain is unavoidable.

We will see with time how the latest firmware for 851 and 871 is doing in that regard.

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> Apparently that was possible in some way with different ADSL chipsets of firmware.

> I personally think the method used (tinkering with the noise margins) was

> obscure and not-standard.

I'd agree it was obscure, but then so was the old analogue "AT" command set that allowed you to do the same on the old V34 modems. However I'm not sure you could call it non-standard, after all increasing the noise margin is exactly what you want to do if you suffer from retrains.

> But, in reality it should be the ISP to cap down the speed when measurements

> shows that high speeds are not reliable.

I disagree because once again we are on a subjective measurement of what is acceptable reliability. A user browsing the web will hardly notice a retrain, a user making heavy use of VOIP almost certainly will.

In the UK, ISPs don't have control over the DSLAMs, therefore any "tweaking" over the standard automated process has to be done on the users router. The cisco 837 was one of the few routers that provided this, it is a great disappointment that the 877 doesn't offer this feature.