DHCP not issuing addresses



  • Hi All

    I am having an isssue on our pfsense box at the moment with the dhcp service. It is failing to issue dhcp addresses to clients on the network. All was working ok on the box up till yesterday. The DHCP logs at the moment currently look like this

    Jan 24 13:20:23 dhcpd: DHCPDISCOVER from 00:0b:82:3c:61:86 via xl0
    Jan 24 13:20:23 dhcpd: DHCPDISCOVER from 00:23:54:1e:f8:23 via xl0
    Jan 24 13:20:22 dhcpd: DHCPOFFER on 192.168.24.210 to 00:d0:4b:8c:81:b3 via xl0
    Jan 24 13:20:22 dhcpd: DHCPDISCOVER from 00:d0:4b:8c:81:b3 via xl0
    Jan 24 13:20:22 dhcpd: DHCPOFFER on 192.168.24.53 to 00:0b:82:3c:61:8b via xl0
    Jan 24 13:20:22 dhcpd: DHCPDISCOVER from 00:0b:82:3c:61:8b via xl0
    Jan 24 13:20:20 dhcpd: DHCPOFFER on 192.168.24.51 to 00:0b:82:3c:61:7d via xl0
    Jan 24 13:20:20 dhcpd: DHCPDISCOVER from 00:0b:82:3c:61:7d via xl0
    Jan 24 13:20:19 dhcpd: DHCPOFFER on 192.168.24.52 to 00:0b:82:3e:78:21 via xl0
    Jan 24 13:20:19 dhcpd: DHCPDISCOVER from 00:0b:82:3e:78:21 via xl0
    Jan 24 13:20:18 dhcpd: DHCPOFFER on 192.168.24.210 to 00:d0:4b:8c:81:b3 via xl0
    Jan 24 13:20:18 dhcpd: DHCPDISCOVER from 00:d0:4b:8c:81:b3 via xl0
    Jan 24 13:20:17 dhcpd: DHCPOFFER on 192.168.24.50 to 00:0b:82:3c:61:7f via xl0
    Jan 24 13:20:17 dhcpd: DHCPDISCOVER from 00:0b:82:3c:61:7f via xl0
    Jan 24 13:20:17 dhcpd: DHCPOFFER on 192.168.24.51 to 00:0b:82:3c:61:7d via xl0
    Jan 24 13:20:17 dhcpd: DHCPDISCOVER from 00:0b:82:3c:61:7d via xl0
    Jan 24 13:20:16 dhcpd: DHCPOFFER on 192.168.24.210 to 00:d0:4b:8c:81:b3 via xl0
    Jan 24 13:20:16 dhcpd: DHCPDISCOVER from 00:d0:4b:8c:81:b3 via xl0

    essentially repeating over and over again.

    I have cleared the logs to restart the service on several occasions but to see if I could see some error information but all looks well in those logs as well

    Jan 24 13:25:09 dhcpd: Sending on Socket/fallback/fallback-net
    Jan 24 13:25:09 dhcpd: Sending on BPF/xl0/00:01:02:9e:53:49/192.168.24.0/24
    Jan 24 13:25:09 dhcpd: Listening on BPF/xl0/00:01:02:9e:53:49/192.168.24.0/24
    Jan 24 13:25:09 dhcpd: Wrote 0 leases to leases file.
    Jan 24 13:25:09 dhcpd: Wrote 0 new dynamic host decls to leases file.
    Jan 24 13:25:09 dhcpd: Wrote 0 deleted host decls to leases file.
    Jan 24 13:25:09 dhcpd: For info, please visit https://www.isc.org/software/dhcp/
    Jan 24 13:25:09 dhcpd: All rights reserved.
    Jan 24 13:25:09 dhcpd: Copyright 2004-2012 Internet Systems Consortium.
    Jan 24 13:25:09 dhcpd: Internet Systems Consortium DHCP Server 4.2.4-P1

    I thought it might be an issue with the drive filling but if I run df all looks ok to me

    Filesystem    Size    Used  Avail Capacity iused ifree %iused  Mounted on
    /dev/ad0s1a    2.9G    235M    2.4G    9%    6.5k  394k    2%  /
    devfs          1.0K    1.0K      0B  100%      0    0  100%  /dev
    /dev/md0      3.6M    48K    3.3M    1%      24  742    3%  /var/run
    devfs          1.0K    1.0K      0B  100%      0    0  100%  /var/dhcpd/dev

    Version information is as follows

    2.0.2-RELEASE (i386)
    built on Fri Dec 7 16:30:38 EST 2012
    FreeBSD 8.1-RELEASE-p13

    I would really suggestions from anyone …


  • Rebel Alliance Global Moderator

    You do notice the dhcp server sending out the offer

    Jan 24 13:20:17    dhcpd: DHCPOFFER on 192.168.24.51 to 00:0b:82:3c:61:7d via xl0
    Jan 24 13:20:17    dhcpd: DHCPDISCOVER from 00:0b:82:3c:61:7d via xl0
    Jan 24 13:20:16    dhcpd: DHCPOFFER on 192.168.24.210 to 00:d0:4b:8c:81:b3 via xl0
    Jan 24 13:20:16    dhcpd: DHCPDISCOVER from 00:d0:4b:8c:81:b3 via xl0

    So is the client seeing this offer?  Do a sniff, look in the offer after you sniff what is wrong with it?

    Client sends discover, dhcpd sends offer – client should then send back request for that offer, then server sends back ack and says sure here is your lease duration, etc.

    Seems your clients are never sending request, or never seeing the offer in the first place even though from the logs they are being sent.

    here is example
    Jan 23 18:34:00 dhcpd: DHCPACK on 192.168.1.230 to 8c:2d:aa:cc:e1:32 via em0
    Jan 23 18:34:00 dhcpd: DHCPREQUEST for 192.168.1.230 (192.168.1.253) from 8c:2d:aa:cc:e1:32 via em0
    Jan 23 18:33:58 dhcpd: DHCPOFFER on 192.168.1.230 to 8c:2d:aa:cc:e1:32 via em0
    Jan 23 18:33:58 dhcpd: DHCPDISCOVER from 8c:2d:aa:cc:e1:32 via em0

    read from bottom up - you see the discover, then server sends offer, clients sends back request, then server sends back ack.  From your logs your sending out the offer but never getting back the request.  So either something wrong in the offer that the client doesn't like or he is not seeing it? Or he is and your not seeing the request?


  • Rebel Alliance Developer Netgate

    Or they're getting a response from another DHCP server and using that instead.


  • Rebel Alliance Global Moderator

    ^ I don't think so, see in the log that :b3 box sent out 3 discovers.  If he grabbed a different lease why would he be sending out discovers still?


  • Rebel Alliance Developer Netgate

    Hard to say with any certainty without capturing on the client.



  • It shouldn't be a case of another DHCP server on the LAN. I will initiate a packet capture on the client and see if I can see what is happening on that end.



  • ok so we have a Netgear FS728TP on the LAN as the main switching device. Devices on static IP's could pass traffic across it to each so hence me not thinking that this might be the issue. On a long shot I decided to have it factory reset … Low and behold I have DHCP leases being supplied.

    Thanks to all for your input and apologies for having wasted your time to some degree. I am off switch shopping now.

    Thanks again,
    John



  • Thank You.

    I have been pulling my hair out with this one, too. Then I saw this post and tried swapping out an old linksys switch.. Lo and behold, everything started working! The whole family are happy!


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