Cisco 857W ADSL Connection Problems

If your Cisco 857W has been working away without problem, and then one day fails to connect, this may help you.


Symptoms
CD (Carrier Detect) light flashes continuously; no PPP (Point-to-Point Protocol) indicated.
(In normal operation both of these should be on continuously).

Disclaimer
Note that you use the steps and commands outlined in this document at your own risk.

Context
My ISP indicated that there had been work carried out in my local telephone exchange, but could not tell me exactly what had changed. Tech support told me that they suspected my equipment - I didn't believe them! When you've worked tech for a few years you get a sense for these things. No option but to go hunting......

After evaluating the various configuration parameters of my beast, focus centred on the dsl operating-mode parameter. The value of this parameter defines how the router will 'talk' to the DSLAM (Digital Subscriber Line Access Multiplexer) located in the telephone exchange.

Solution
The solution to my problem was to alter the value of the dsl operating-mode parameter from auto to ansi-dmt.

I'll give a brief outline of the steps required to do this - if you're really desperate for more detail you'll have to drop me an email and I'll do my best to help: red@redosaka.com. To make these configuration changes you should forget about using SDM (the Cisco supplied Web Interface application) and instead use HyperTerminal- a command line interface that comes free with Windows.

Once you have HyperTerminal installed/configured, ensure your router is turned OFF, and then launch HyperTermimal (All Programs -> Accessories -> Communications -> HyperTerminal).
In HyperTerminal:
1) Set up a connection to your router (you can save it, suitably named, for future use), and connect.
2) Now turn your router on. You should see a series of boot-up, version, rights, and copyright messages, before you see the message "Press RETURN to get started!".
3) Press the Return key, and enter your username and password.
4) View your existing running config by entering show running-config.

You now need to alter the running config to see if you can find a setting that works e.g. ansi-dmt, itu-dmt, etsi - the options available to you will depend on the exact make and model of your router. Once you've found a setting that works, you then need to apply it to the startup config. If you only amend the running config the change will last only until you turn off the router. Note the identifier of the ATM interface that you want to change e.g. ATM 0.

5) Change the value of the dsl operating-mode parameter in the running configuration by entering the following command sequence:

conf t
int atm 0
dsl operating-mode itu-dmt
end

At this point wait a minute or two while your router tries to connect using the new value. If it doesn't connect, try another value. If it does connect you need to copy the running config to the startup config to retain the change.

6) Saving your new configuration, by issuing the command:

copy running-config startup-config

When the text Destination filename [startup-config]? appears, just press return (causes the default startup-config file to be overwritten).
You should then see then see the following messages appear:

Building configuration...
[OK]


Now check the startup configuration by entering:

show startup-config


If your changed setting shows as you specified, you're done. Enter logout at the command prompt and then click the disconnect icon on the HyperTerminal toolbar.

Disclaimer
Note that you use the steps and commands outlined in this document at your own risk.