[lug] tcpdump, routing, ppp, and cable modem questions(s)
John.Hernandez at noaa.gov
Mon Mar 15 10:34:22 MST 2004
Chip, AFAIK, those modems are usually set up in bridging mode, which
means your PC will need to send out the DHCP request. As I recall, it
also required you to send a hostname along with the request. I'm not
sure if that is still the case, as my connection was on the old ATTBI
Chip Atkinson wrote:
>Dang. Ok. I'll have to see if I can round up a windows machine for a
>About the DHCP, that is on the cable end of the modem, so I shouldn't have
>to worry about that, right?
>Thanks for the information too.
>On Mon, 15 Mar 2004, Ferdinand Schmid wrote:
>>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
>>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.
>>--On Monday, March 15, 2004 08:25:44 AM -0700 Chip Atkinson <chip at rmpg.org>
>>>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)
>>>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
>>>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
>>>Thanks in advance.
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