Re: Is it possible to record a DHCP handshake?

From: Tauno Voipio (tauno.voipio_at_iki.fi.NOSPAM.invalid)
Date: 12/06/04 

Date: Mon, 06 Dec 2004 15:15:47 GMT

Elias Aarnio wrote:
> Hello,
>
> It is very common among the ISP's to refuse any responsibility even if
> there is a malfunction in their hardware devices. A very common problem
> these days is low-end HomaPNA switches that all of the sudden stop
> functioning as DHCP servers.
>
> This causes all clients (customer's computers) behind that switch to be
> unable to use the connection. These "layman" HPNA services often also
> state in the user guide that the the ISP has the right to change the IP
> addresses of the default gateways etc. without prior notice.
>
> So, when I go to help somebody with a problem like this, I would like to
> "record" the DHCP handshake. This would be extremely useful when the
> customer wants to get his/her money back from the ISP.
>
> How do you record a DHCP handshake?
>

The sure-fire method is a hub (not switch) and another
computer to catch the traffic.

Lacking that:

You have to be root on the computer.

Use ifconfig to get the interface up, then start tcpdump
(or whatever sniffer) on it. Start the DHCP client manually
after the capture tool is up.

If the tool refuses to start capturing, get the interface
up with IP address of 0.0.0.0

My favourite sniffer is Ethereal (or tethereal if no graphic
environment is available).

HTH 

-- 
Tauno Voipio
tauno voipio (at) iki fi

Relevant Pages

  • Re: How to create a shareable image on IA64 using Pascal
    ... There is nothing wrong with "COMMON" areas and shared PSECTs! ... Even something as simple as setting switch variable can be fraught ... - the fact of the global storage was hidden behind an API (or at ... that was supposed to support multiple terminals. ...
    (comp.os.vms)
  • Re: Newsreader: Best of the bunch?
    ... I'm talking about COMMON functions such as ... which gives me that, I'll switch to it. ... When I use another editor, I constantly hit wrong keys, ...
    (Debian-User)
  • RE: Wired captive portal pen-test
    ... I've done similar voipsec audits at hotels. ... think) they are identifying my room by the switch port (I cannot figure ... Or are they deployed using common hardware ... Securing Web Applications ...
    (Pen-Test)
  • Re: Wired captive portal pen-test
    ... but the Nomadix is deployed as a Gateway with a ... switch you're plugged is configured to deny that. ... Or are they deployed using common hardware ... Top 5 Common Mistakes in Securing Web Applications ...
    (Pen-Test)
  • Re: Wired captive portal pen-test
    ... I've used a Nomadix system. ... but the Nomadix is deployed as a Gateway with a ... switch you're plugged is configured to deny that. ... Or are they deployed using common hardware ...
    (Pen-Test)