Cisco 1841 ADSL2 Noise Margin Fluctuating


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.

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George K.Commented:
I have read somewhere a similar case that got solved after a very recent firmware upgrade.
What 's your version?
sparky2156Author Commented:

How do I check the version of firmware I have?

George K.Commented:
show version
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sparky2156Author Commented:
Version 12.4(15)T12.

I dont have a cisco technical support contract, so how will i be able to get a firmware upgrade?

George K.Commented:
I have  searched around,
and there seems to be an issue with BT ADSL 2 with Cisco routers.

 You should upgrade the modem firmware. If you have a contract you should have no problem getting it then

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George K.Commented:
Here is the place to search
George K.Commented:
sparky2156Author Commented:
How are you meant to know which to go with?


I cannot afford to brick this router as its miles away and very important.
George K.Commented:
ED=Software releases that provide new features and new platform support in addition to bug fixes
MD=A Cisco software release that provides bug fix support and ongoing software maintenance.
Read this:
You can copy a startup configuration file onto the CF card.
 Note that while Cisco routers load their firmware from the CF card, router configuration is loaded from NVRAM (nonvolatile RAM), so the router configuration can't be directly booted from the CF card. But you can copy the configuration file from the CF card to NVRAM to recover a configuration file or do it in the reverse direction to back up a configuration.
and this:
Here is your list to choose from see table 2:
However you do it, be sure you have saved the proper backup of the configuration etc.
Since you are away from the router 's site,
here are some usefull hints/commands:
have in mind that the router tries to boot first from image in the onboard system Flash,
 then,  from PCMCIA Flash cards. 
 You can also specify which images/locations to boot from and the also order with the boot system command (whil in configuration mode):
# boot system slot0
To have the router reload in case of problems automatically after a specified period of time, use the command:
# reload in 10
this will automatically reload the router in 10 minutes. That is if you lose/cannot "see" your router during the proceess it will reboot with the old configuration in 10 minutes anyway.
That is, the router 's configuration. It will not revert the new IOS you might have installed.
Also you shouldn 't save any config at this point.
If everything is ok the issue the command:
# reload cancel 

to cancel the router reload.

sparky2156Author Commented:
Hi georgekl,

First off - this is a Cisco 1801 router - apologies.

I have done some more investigation from your comment about it being a known fault, detailed here:;jsessionid=55654CFEC9FD231201343E8721581747.node0

When i run 'sh dsl int atm 0' I see that the FW Source is embedded and FW Version is 3.0.14.
It would appear that I need to upgrade the firmware to 4.0.018.

Given that the firmware is 'embedded', and that entering 'dir' shows a bunch of files, including the IOS image, but no ADSL Firmware file, I take that the firmware is built into the IOS on these Cisco 1801 routers. It is worth mentioning that the router is in its default state, so the adsl port is built into the chassis as opposed to being an optional WIC.

A show version on my router shows I have the following IOS/Firmware:

c180x-advipservicesk9-mz.124-15.T12.bin  (Release Date: 25/Jan/2010)

I can see a bunch of IOS upgrades on the cisco website for this router, and the most up-to-date IOS which seems to be the best match is:

c180x-advipservicesk9-mz.151-2.T1.bin (Release Date: 17/Aug/2010)

Or my second option

Go back down to ADSL 8mb from my existing ADSL2 20mb connection. This will take 3 working days.

If i go with the new firmware, which i need a technical support contract first with cisco, would i be better doing this while i am infront of the router with a console cable? If so, what procedure should I follow?

George K.Commented:
I would recommend you make a technical contract with cisco.
Then you will have the options to solve your problem and also have some assist from the manufacturer itself.
The procedure wouldn 't change from what I described above.
Before starting plan well the steps you and method you wish to follow.
Don `t just go there and do it. Plan and be sure you know the most procedures, in case something goes wrong/restore etc. This will save you a lot of headache - just in case. 
Yes, you should do it  at the router 's site.

sparky2156Author Commented:
This is an ongoing issue with BT ADSL2. You can get a downgrade to ADSL 8mb or get the most up to date firmware - which i dont have access to.
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