ISR 877 with BT ADSL

Unanswered Question
Jul 24th, 2009

I have an 877 which is configured to work on a BT Business ADSL connection. The problem is that the connection drops every few weeks or so.

I have just wiped the config, upgraded to the very latest IOS and would simply like somebody to tell me how to configure the ADSL connection correctly.

I'm using the 877 in conjunction with an ASA 5505, so don't want the router to provide any firewall functionality.

Thanks in advance for any help on this...

Campbell

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Giuseppe Larosa Sat, 07/25/2009 - 12:34

Hello Campbell,

>> The problem is that the connection drops every few weeks or so.

but it is a short time outage?

I would contact the service provider.

However you may like to check the healthy of your line.

You can do this with:

sh dsl interface atm0

take this from time to time to collect information.

each line has its own characteristics and there are noisy or disturbed lines that can fall multiple times per day if the the signal to noise is low.

Every speed requires a minimal noise margin (that is a signal to noise ratio) to work well.

Hope to help

Giuseppe

campbell.thomps... Sun, 07/26/2009 - 01:28

Thanks Giuseppe,

It basically drops and then doesn't come back unless I powercycle the 877. I want to get up to the latest IOS (which I've just installed) so I can count out any version problems. I'm contacting the ISP also.

I'm assuming that the line should come back after a drop out if things are working okay?

Do you have any ideas of the best way to configure this line from the 'add interface' wizard?

Giuseppe Larosa Sun, 07/26/2009 - 01:56

Hello Campbell,

>> I'm assuming that the line should come back after a drop out if things are working okay?

when your modem and CO modem are able to negotiate again (for example noise or interferences are back to values they can deal with) the line should be up again.

What you said about the need to power cycle makes to think you may need a different modem firmware. One way to update it is by IOS image upgrade.

The other way is by downloading and writing to flash the modem firmware.

>> Do you have any ideas of the best way to configure this line from the 'add interface' wizard?

I haven't used SDM up to now.

However, there are configuration examples on CCO and you can check the config with

sh run int atm0 from shell.

if you like next time the line is stucked, before power cycling get a telnet or console access to the device and get

sh dsl int atm0

sh log

sh proc cpu | inc util

sh proc mem | inc Free

save all this to a text file that you can attach to a message in this thread.

Hope to help

Giuseppe

campbell.thomps... Sun, 07/26/2009 - 02:14

Thanks Giuseppe,

I've now upgraded the IOS to the very latest version, so I'm hoping this will assist with the reconnects.

I'll let you know how I go.

Thanks again.

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