pppd stops communicating with modem on ttyS1after a minute or two

[John]

Doubletwist wrote:
> Neil Woolford wrote:
> 
>> Hi,
>>
>> I'm trying to use a dialup connection with Ubuntu.
>>
>> I can connect to my ISP as normal, but then I get a failure of the 
>> connection after three to eight minutes.
>>
>> In /var/log/messages I find the following lines from pppd;
>>
>> No response to 4 echo requests.
>> Serial link appears to be disconnected.
>> Connection terminated.
>>
> 
> Since you say everything works fine under other environments, that 
> messages makes it seem like it's trying to ping the other side and not 
> getting a response.

Those would be ppp echo requests, not IP echo requests aka pings. The 
firewall won't be blocking them, but line problems will.

Tis hard to be more helpful, this is one of those problems I like to 
leave alone unless it's _my_ system and I've got my hands on it,

You could man pppd and turn on whatever pppd options seem good. One I 
like is to record to a file and print it out later with pppdump.

Do remember to turn it off later, it creates quite a big file. Specially 
if you dist-upgrade far.