Problems with Fedora and cable modem

Jeff Vian jvian10 at
Tue Nov 30 01:19:02 UTC 2004

On Mon, 2004-11-29 at 10:51 -0600, Aleksandar Milivojevic wrote:
> I have a problem with my Fedora box and cable modem.  I'm not sure if 
> the problem is on my side, or ISP side (Shaw cable).  Of course, ISP 
> claims it is not them, what else would you expect ;-)
> Basically, what happens is that dhclient obtains IP address for my 
> external interface.  Than everything works fine for some period of time 
> (less than a half an hour), and after that I loose all Internet 
> connectivity.  If i restart dhclient (for example using "ifdown eth0; 
> ifup eth0"), my PC gets IP address reassigned (in my case, I'm always 
> getting same address,, everything works for a while, and 
> than it stops again.
> Something like this happened about a month ago, and restarting the 
> interface solved the problem.  Yesterday it started to happen again, but 
> this time restarting the interface solves the problem for about a half 
> an hour, and than there it is again...
> I have two more interfaces on this Linux box.  One is toward my internal 
> network, and another is toward DMZ.  Those two have static IP addresses, 
> and everything seems to be working fine with those two.
> What I have observed when this happens, is that I can sometimes ping the 
> router on ISP side (, but nothing else.  Sometimes. 
> Sometimes ping to ISP router doesn't work at all, or works partially 
> with large percentage of lost packets (95-99% range).
> Anybody else had similar problem?

This description is typical of a noisy or marginal quality cable. 
I have seen this when something else is attached to the same cable, or
when a connector on a cable end is going bad.

What you did not say, is whether you have power cycled the modem.  This
often works for me. I also have seen similar problems when the modem was
losing sync, and in one case when it was failing. That time, a new modem
fixed it.

Of course, as we all know; weather, rain, etc. has no affect on signal
quality on cable.  It could not possibly be the cable signal. <sic>.
When all else fails, if you own the modem try a replacement.  If you are
renting the modem from the cable company, try a replacement.

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