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I have a dhcp server here, running the isc-dhcpd daemon.

Some machines get an IP address fine, from syslog:

Dec  8 08:42:21 nethandler dhcpd: DHCPDISCOVER from 90:e6:ba:f6:xx:xx via eth0
Dec  8 08:42:21 nethandler dhcpd: DHCPOFFER on 10.0.0.202 to 90:e6:ba:f6:xx:xx via eth0
Dec  8 08:42:21 nethandler dhcpd: DHCPREQUEST for 10.0.0.202 (127.0.1.1) from 90:e6:ba:f6:xx:xx via eth0
Dec  8 08:42:21 nethandler dhcpd: DHCPACK on 10.0.0.202 to 90:e6:ba:f6:xx:xx via eth0

Others don't

Dec  8 08:42:04 nethandler dhcpd: DHCPDISCOVER from 08:00:27:d5:xx:xx (WIN-3053MGTDBGP) via eth0
Dec  8 08:42:04 nethandler dhcpd: DHCPOFFER on 10.0.0.132 to 08:00:27:d5:xx:xx  (WIN-3053MGTDBGP) via eth0
Dec  8 08:42:08 nethandler dhcpd: DHCPDISCOVER from 08:00:27:d5:xx:xx  (WIN-3053MGTDBGP) via eth0
Dec  8 08:42:08 nethandler dhcpd: DHCPOFFER on 10.0.0.132 to 08:00:27:d5:xx:xx  (WIN-3053MGTDBGP) via eth0

And continue ad infinatum. I can't find any pattern to the machines that can't connect. Some wireless clients can't connect, some can. An ubuntu vm can connect, a windows 7 vm on the same hardware can. A windows server on the same hardware can't. A few macs here can't.

Any help would be appreciated, or a point to what I can use to further debug the problem.

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2 Answers

up vote 1 down vote accepted

Try doing a packet capture on the client. dhcpd thinks it's sending out an OFFER, either the client is ignoring it or (more likely) the offer never makes it to the client.

While you're at it, also do a packet capture on the server, and if you can, on something in-between (a SPAN/Mirror port on the switch, router port, etc.).

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I have solved the problem. server-identier was incorrectly set in my dhcpd.conf, so the DHCPACK's would have been incorrectly addressed. Updated that and everything went. Thankyou. –  richo Dec 7 '10 at 22:18
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Look for a DHCP rogue server on your network. There is a free microsoft tool to search. Also, make sure you are using IPhelpers on your switches.

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No rogue servers, or evidence that there were. I'm not sure what made you think there would have been? –  richo Dec 7 '10 at 23:45
    
IP helpers are on routers, not switches. If the DHCP server has an interface on the network, IPhelper is not needed. –  Jason Antman Dec 8 '10 at 18:19
    
As to rogue DHCP servers, no need for a Microsoft tool, just tcpdump for DHCP traffic and look at the source ports. –  Jason Antman Dec 8 '10 at 18:19
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