[Beowulf] Re: OT: PXE boot with no control over DHCP?

Joe Landman landman at scalableinformatics.com
Thu Sep 22 10:05:59 PDT 2005

Hi David:

   In terms of figuring things out, run ethereal or tcpdump on the net 
to see if you are getting any DHCP packets.  If the don't show up, then 
you have a problem.  If you are running the ISC dhcp server, make sure 
it is listening on the right interface.

   Usually one of the "smart" switches gets in the way of doing the 
right thing.  If the switch is set to discard all multicast traffic, or 
plays games with spanning trees or other bits you might have a problem. 
  If your server is somehow on a different vlan as the workstation, you 
will also have a problem.

   If you can boot knoppix but not get an IP address, set it to an empty 
one (you should have a small pool of empty ones just for these cases), 
and try pinging your server.  If the pings get through, you should be 
able to send udp pings .


David Mathog wrote:
>> 1) Set up your own dhcp server and make sure you have all the mac
>> addresses for your hosts so that your server only offers addresses to
>> your clients and no one else.
> Did that.  Also punched holes in the firewall for dhcp and tftp.
>> 2) Make sure these hosts are on the same router or switch as your dhcp
>> server so your server manages to offer an address first, before the
>> campus dhcp that you don't manage.
> Here's where things go south.  I don't see any evidence
> of the dhcp packets from the booting workstation reaching
> the server.  Even with the firewall turned off nothing
> shows up in the log files and the workstation client times out.
> I also tried booting knoppix on the machine, because
> it uses dhcp to find it's IP address, but the one it came up
> with was from the campus DHCP server and not my DHCP server.
> Perhaps I have something wrong in the dhcpd.conf. Other than
> a typo this is fairly unlikely, it was modified from the working
> version that runs on the private subnet. Moreover the config
> eliminated the "Ignoring requests on eth0" message starting dhcp
> used to elicit, so the dhcpd does seem to have been ready to
> handle a request, if it ever saw one.  It seems that the
> campus network may really by blocking at the switch dhcp
> requests from reaching any but their servers. 
> The workstations in question have an MBA which offers
> 4 network boot options: PXE, tcp/ip, netware, and RPL.  
> PXE seems to be out and I'd rather not start a netware
> transport on the main server just for  this purpose (assuming
> it's even possible.)  That leaves tcp/ip
> (presumably bootp?) and RPL (which I've never even heard of
> before).  Any thoughts on getting one of those two to work with DHCP
> blocked?  
> Thanks,
> David Mathog
> mathog at caltech.edu
> Manager, Sequence Analysis Facility, Biology Division, Caltech
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Joseph Landman, Ph.D
Founder and CEO
Scalable Informatics LLC,
email: landman at scalableinformatics.com
web  : http://www.scalableinformatics.com
phone: +1 734 786 8423
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