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

[John Hernandez]

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 
network.

Chip Atkinson wrote:

>Dang.  Ok.  I'll have to see if I can round up a windows machine for a
>little while.
>
>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.
>
>Chip
>
>On Mon, 15 Mar 2004, Ferdinand Schmid wrote:
>
>  
>
>>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
>>
>>_______________________________________________
>>Web Page:  http://lug.boulder.co.us
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>>
>>    
>>
>
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>  
>

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