Help: Frequent DHCP disconnects



  • One device on my network gets disconnected every couple of hours. I found a thread that said the following: "if you look at the dhcp lease file and find two leases for the same mac adress deleat one to fix the problem". So i did what the thread suggested. Didn't work. Same mac adress got a double lease again. Can someone help me solve this please?
    This is what sys log dhcp says:
    Sep 22 23:11:39 dhcpd: DHCPDISCOVER from MACADRESS via nfe0
    Sep 22 23:11:39 dhcpd: unexpected ICMP Echo Reply from PUBLIC IP
    Sep 22 23:11:40 dhcpd: DHCPOFFER on 10.1.2.21 to MACADRESS via nfe0
    Sep 22 23:11:40 dhcpd: DHCPREQUEST for 10.1.2.21 (10.1.2.10) from MACADRESS via nfe0
    Sep 22 23:11:40 dhcpd: DHCPACK on 10.1.2.21 to MACADRESS via nfe0
    Sep 22 23:11:59 dhcpd: DHCPDISCOVER from MACADRESS via nfe0
    Sep 22 23:11:59 dhcpd: DHCPOFFER on 10.1.2.21 to MACADRESS via nfe0
    Sep 22 23:11:59 dhcpd: DHCPREQUEST for 10.1.2.21 (10.1.2.10) from MACADRESS via nfe0
    Sep 22 23:11:59 dhcpd: DHCPACK on 10.1.2.21 to MACADRESS via nfe0


  • LAYER 8 Global Moderator

    why did you hid the mac address?  You do understand that is completely useless for anyone in finding you.  Most we could do with it is tell what hardware it was from the first 3 numbers.

    Why is your client sending discover after he sends out dhcpack saying ok I will take that lease, and then 19 seconds later he sends another discover?



  • @johnpoz:

    why did you hid the mac address?  You do understand that is completely useless for anyone in finding you.  Most we could do with it is tell what hardware it was from the first 3 numbers.

    Why is your client sending discover after he sends out dhcpack saying ok I will take that lease, and then 19 seconds later he sends another discover?

    No i didn't know that's all you can do with a mac adress.
    Even thoug i deleted the double lease. My dhcp lease file looks like this the next day:
    lease 10.1.2.21 {
      starts 3 2015/09/23 21:14:14;
      ends 3 2015/09/23 23:14:14;
      cltt 3 2015/09/23 21:14:14;
      binding state active;
      next binding state free;
      rewind binding state free;
      hardware ethernet 70:9e:29:db:e2:5d;
      uid "\001p\236)\333\342]";
    }
    server-duid "\000\001\000\001\035\224\203\014\000\031f\325VJ";

    lease 10.1.2.21 {
      starts 3 2015/09/23 21:14:34;
      ends 3 2015/09/23 23:14:34;
      cltt 3 2015/09/23 21:14:34;
      binding state active;
      next binding state free;
      rewind binding state free;
      hardware ethernet 70:9e:29:db:e2:5d;
      uid "\001p\236)\333\342]";
    }

    Looks like it's sending a discover request two times because of the double lease. I can't get rid of it.



  • That has nothing to do with the leases contents. The fact it's there multiple times is a symptom of the problem with the client, or the network in between, nothing to do with the cause.

    The client either isn't getting the response from the server, or it's refusing it for some reason, and re-issuing the request. Look at the client, that's where the issue resides.


  • LAYER 8 Global Moderator

    "Looks like it's sending a discover request two times because of the double lease"

    No that is NOT how it works!!!  As cmb stated the issue is on your CLIENT!!



  • How can it be the client? Setting it to a static ip is the only change i can make on the client side. The only thing between client and server is a unmanaged switch.



  • Only the client controls whether and when it sends a DHCPDISCOVER. Either the offer isn't getting back to the client (network in between somewhere is dropping it) or the client is refusing the lease.



  • I guess it's not an dhcp issue after all. Got this today : "a lan cable is not connected".  My wan seems to drop the connection every couple of hours.


  • LAYER 8 Global Moderator

    what would your pfsense wan have to do with a client sending multiple discovers?



  • @johnpoz:

    what would your pfsense wan have to do with a client sending multiple discovers?

    I don't know. The client i mentioned seems to send a discover each time the drop happens, while my pc gives me a dns error for a couple of seconds.



  • Is there no body that can help me with this? A dropping internet connection is the worst.

    Before anyone says it's the client. I did hook up my old  linksys e4200 and did work normally over the weekend.



  • @Isegrim:

    I guess it's not an dhcp issue after all. Got this today : "a lan cable is not connected".  My wan seems to drop the connection every couple of hours.

    That would explain why it's grabbing another lease, it's losing link to the switch it's plugged into. When it re-gains link, it'll request another DHCP lease. That has nothing to do with your WAN connection, and nothing you've shown indicates your WAN is dropping.

    When you switched to the Linksys I'm guessing you changed switches as well, or changed something else about where that client machine's plugged in.



  • That would explain why it's grabbing another lease, it's losing link to the switch it's plugged into. When it re-gains link, it'll request another DHCP lease. That has nothing to do with your WAN connection, and nothing you've shown indicates your WAN is dropping.

    When you switched to the Linksys I'm guessing you changed switches as well, or changed something else about where that client machine's plugged in.

    Yes.
    Before: Pfsense > switch 1 > switch 2 > work pc / console & TV | pfsense > switch 1 > a tv and a couple of other entertainment devices.
    After: Linksys > switch 1 > work pc / console & TV. Everything else is connected wirelessly in this setup.
    i'll get another switch and see if that fixes my issues.


Log in to reply