[X-Unix] How to find your DHCP server...

[Alexandre Gauthier]

William H. Magill wrote:

> On 14 Sep, 2004, at 05:17, Stroller wrote:
>
>> I'm connected to a client's network & trying to confirm which machine 
>> is issuing IP addresses around here. I plug my laptop running 
>> Panther) into the network & am issued a 192.168.x.y address well 
>> enough, but how do I determine where it's come from..?
>>
>> Under the version of Linux I've used the DHCP client is called 
>> `dhcpcd`, and I grep for that in the logfiles. What's the equivalent 
>> in Mac OS X, please..?
>>
>> When I plug the ethernet cable in, this happens in  /var/log/system.log
>>
>> Sep 14 09:58:10 localhost kernel: UniNEnet::monitorLinkStatus - Link 
>> is up at 10 Mbps - Half Duplex
>> Sep 14 09:58:13 localhost configd[123]: posting notification 
>> com.apple.system.config.network_change
>> Sep 14 09:58:13 localhost mach_init[2]: Server 0 in bootstrap d03 uid 
>> 0: "/usr/sbin/lookupd": exited as a result of signal 1 [pid 1069]
>> Sep 14 09:58:13 localhost lookupd[1086]: lookupd (version 324.2.1) 
>> starting - Tue Sep 14 09:58:13 2004
>
>
> Just yesterday, I was just pointed to an interesting tool by an Apple 
> Supportline chap ...
>
> ipconfig getpacket en1   [or which ever interface you are using]
>
> In the middle of the output will be:
>      server_identifier (ip): 10.0.1.1
>
> Naturally, there is no documentation for this tool, but it appears to 
> be similar to the Windows tool.
> So far, I haven't found "the" source for the code. Anybody know if it 
> is in the Darwin tree?
>

Hmm, this is a very interesting idea.
Actually, what could also be done would be running ethereal to figure 
that out, or tcpdump, if it is available.

(Ethereal IS available through fink:
    xerxes:~ supernaut$ fink install ethereal
    /usr/bin/sudo /sw/bin/fink  install ethereal
    Password:
    Information about 3829 packages read in 10 seconds.
    The following package will be installed or updated:
      ethereal )

Just filter for bootp/dhcp packets, you should see the 
DISCOVER/REQUEST/ACK requests with source and destinations...

-- 
Alexandre Gauthier
supernaut at underwares.org

underwares.org
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