[Charlug] Question about cable modem and dhcp

[Kevin]

Hi all,

    Several months ago I signed up for TW RoadRunner broadband cable 
service. The  service is pretty good (moved from dial-up), but I have 
noticed something that seems to be happening a little more frequently 
lately. I apparently loose the connection to the Internet, at apparently 
random intervals. I will notice that a site is not responding, or that a 
new site can't be found. When I check 'route' it hangs, instead of 
giving me back the normal listing with 'default' being the cable modem. 
Since I'm new to using dhcp, I don't know if the problem is on my end or 
RR's end.

The cable modem is an Ambit model (suppled by TW). I'm using a USB 2.0 
interface. I also have a small local ethernet system- standard Linksys 
card to hub (usually only the computer with the cable modem is running 
so the hub is not active). udev finds the cable modem when I boot up, 
assigns it to eth1, and 'dhcpcd -d -t 30 eth1' is run by the inet 
script. I wrote a bash script that will bring the modem interface up and 
down (for extra security, when I finish running a browser, the script 
brings the interface down, and back up when I start the browser). The 
script just does 'ifconfig eth1 down' or 'ifconfig eth1 up' and restarts 
inet1. Both times 'route' is executed to make sure the commands have 
gone through. When I lose the Internet connection, I run the script from 
a terminal window to reset everything. I'm not getting any error 
messages from the usb interface.

My problem/question is that I don't know exactly what is happening. I 
can go for days with losing the Internet (I'm on a total of several 
hours a day), or this can happen once or several times a day. I tried 
lengthening the dhcpcd timeout to 45 seconds, but so far that does not 
seem to have had any effect. Has anybody seem a similar problem, or can 
anybody point me in a direction to try to find the cause? The dhcp log 
doesn't tell me much. Thanks,

        Kevin