[lug] tcpdump, routing, ppp, and cable modem questions(s)

[Ferdinand Schmid]

Chip:

You will need to use Internet Explorer to get to the registration site for
Comcast.  I have gone through this exercise and found that they really require
IE.  Also - dhcp in their cable modems doesn't necessarily work with every
computer.  I had a terrible time with it on my PC - couldn't get it to work on
a Dell laptop under Linux or Windows.  However, a D-Link router was able to
talk to it.  Strange...  So my approach to get it working was to use a USB
cable combined with a Windows PC to do the modem registration.  Until this is
complete you will only be able to get to your cable modem and to Comcast's DNS
servers.  

So - find a Windows PC to register the modem and then connect your Linux
system.  If you can't get dhcp working with your particular modem then just
pick your IP address manually.  The default route (your cable modem's local
IP) never changes anyway.

Ferdinand

--On Monday, March 15, 2004 08:25:44 AM -0700 Chip Atkinson <chip at rmpg.org>
wrote:

> Greetings all,
> 
> I recently signed up for internet access through Comcast, the cable TV
> provider and am trying to get my machine connected to it.  During the
> process I came across/caused a couple problems and also can't connect out
> to anything past the cable modem.
> 
> Here are the problems:
> 1) the ppp0 interface has disappeared.  It was working that morning but
> now is gone.
> Using kppp I get an error saying
> ppp: no such interface (don't remember the exact wording)
> and
> ifconfig ppp0 up
> returns ppp0: unknown interface: No such device.
> 
> 2) I was using tcpdump to watch network traffic on eth0.  When there was
> no default route set, I saw tons of ARP requests from other machines, but
> when I set the default route: route add default gw 192.168.100.1 (the
> cable modem's IP), the ARP request traffic wasn't visible suddenly.  When
> I deleted the default route, the traffic was visible again.
> I thought tcpdump grabbed all of the traffic, regardless of routing
> tables.
> 
> 3) I'm unable to get to a web server on the Comcast network to register
> and get to the internet and I fear that it's due to something weird that
> also caused ppp and the weird tcpdump behavior.  I can ping the WAN end of
> the cable modem, but nothing else.
> 
> Does anyone have any similar experiences or ideas?  Right now I'm kind of
> stumped.
> 
> Thanks in advance.
> 
> Chip
> 
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--
Ferdinand Schmid
Architectural Energy Corporation
Celebrating over 20 Years of Improving Building Energy Performance
http://www.archenergy.com