Q&A: Dropping Internet connection and LCP

Q Previous Internet connection problems have returned, with frequent loss of connection. Checking the modem-router logs, I see that disconnection coincides with times that there are entries recording “LCP down”. What do those mean, and how can I fix them?

A LCP is the Link Control Protocol, used between your router and the exchange to keep your broadband line in sync. When it goes down, there is a disconnection between router and exchange, and traffic will not get through until the log records that LCP has come back up.

Classic explanations for this include line noise, a line fault, and router problems.

Line noise can occur when local heavy electrical equipment starts up or shuts down, causing electromagnetic interference, or because the connection within your premises is old or infirm.

Duff lines are the concern of your phone or services provider’s engineers, who need to perform tests on the line.

Older routers may not be able to cope with the speed that the line can work at, or may not be fully compatible with newer ADSL2+ techniques. Replace any old microfilters and suspect cabling and get an engineering check on your line before considering replacing the modem-router.

Updated from the original, which was first published in MacUser volume 28 issue 15, 2012.