PXE DHCP server without interfering with the "real" server?

Message

vputz · Post by **vputz** » Tue Feb 14, 2006 2:12 am

I'd like to experiment with DHCP and PXE boot (so I can use my wife's desktop and laptop as distcc zombies, muhahahaaaa!). I'd also like to avoid screwing with my home network as much as I can. I have a WRT54G running Linux (dd-wrt) but for whatever reason I can't seem to get its dnsmasq server to do PXE boot correctly, but I need it to do most of the DHCP (since it's serving as the wireless gateway and I screw with my server a lot more than I screw with the router--it'd be nice if the router were stable).

Is there a way to set up a DHCP server on the gentoo server that only handles pxe requests and leaves everything else to the router?

Thanks-->VPutz

JeliJami · Post by **JeliJami** » Tue Feb 14, 2006 9:16 am

in our network, we have a regular dns server, that provides the desktops with ip settings
this dhcp server is installed on our router

in this same network, we have a second dns server, that provides for PXE boot clients
it is a Debian system, with dhcp3-server (v3.0.3-5) installed

make sure both dhcp servers provide addresses that do not collide (we are using a separate range for each)

on the 'PXE server', the /etc/dhcp3/dhcpd.conf file has the following entry:

Code: Select all

deny unknown-clients;

this, of course, means that the mac addresses for the PXE clients must be known and inserted into this conf file

we had no conflicts, or PXE boot problems so far

rabinath · Post by **rabinath** » Tue Feb 14, 2006 9:24 am

I have a similar setup with a wrt54g (openwrt) and made it work. My problem was an old PXE-Rom that didn't honor the address auf the tftp-server - wich is on another machine - but insisted on loading tftp from the same address as the dhcp-server. I updated the PXE of my 3com card (http://support.3com.com/infodeli/tools/nic/mba.htm) to make it work. You find other information about PXE updates at http://syslinux.zytor.com/hardware.php#network.

vputz · Post by **vputz** » Tue Feb 14, 2006 2:29 pm

Davjel, this sounds great. One question--if I boot one of those systems without PXE (but same MAC address!) will it be able to get a regular DHCP assignment, or will it be confused since it didn't boot PXE? Which server will it go scurrying off to?

Thanks! Good info; I really appreciate it.

JeliJami · Post by **JeliJami** » Tue Feb 14, 2006 4:43 pm

vputz wrote:if I boot one of those systems without PXE (but same MAC address!) will it be able to get a regular DHCP assignment, or will it be confused since it didn't boot PXE? Which server will it go scurrying off to?

got me there

i guess it will get an address from the dhcp server that answers first

davidblewett · Post by **davidblewett** » Tue Feb 14, 2006 7:57 pm

This might seem overkill, but using a 2nd NIC in the machine hosting the PXE server might resolve that. I.e., only plugin to that side when you want to do PXE, otherwise use 1st.

DHCP is not easily controlled like this. Your client will accept the response from the first server to respond. That's why LAN parties usually require DHCP to be turned off on all machines attending. It can cause havoc in a network.

think4urs11 · Post by **think4urs11** » Tue Feb 14, 2006 8:51 pm

you could try to use dhcp-client-identifiers on either your routers dhcp or your servers dhcp - whatever fits best in your situation.

So you can diffentiate between 'normal boot' (e.g. with identifier 'i wanna work') and 'pxe boot' (without special identifier and thereby using the default, the NICs MAC).

JeliJami · Post by **JeliJami** » Wed Feb 15, 2006 7:30 am

when booting locally, you could use iptables to block the dhcp offer from your pxe server