dhclient requesting the IP address too many times

zweistein · 04-23-2008, 06:03 AM

Hello.

I've been informed by my network administrator today that my machine sends too many requests for an IP address to the DHCP server, and that I should fix that ASAP.

I've been searching around and found some people with similar problems, but couldn't find a solution. I'm connecting to a wired network, authenticating with wpa_supplicant and requesting an IP address with dhclient (I have a script that runs wpa_supplicant and dhclient at startup).

Here is an excerpt from my /var/log/syslog:

Code:

Apr 23 07:42:21 nyx dhclient: DHCPREQUEST on eth0 to 10.3.x.x port 67
Apr 23 07:42:51 nyx last message repeated 3 times
Apr 23 07:43:48 nyx last message repeated 4 times
Apr 23 07:44:39 nyx last message repeated 3 times
Apr 23 07:45:52 nyx last message repeated 6 times
Apr 23 07:46:33 nyx last message repeated 3 times
Apr 23 07:47:47 nyx last message repeated 4 times
Apr 23 07:48:10 nyx last message repeated 2 times

As you can see, it sent 25 requests in a couple of minutes, and a few of them in really short time intervals.

Here is my /etc/dhcp3/dhclient.conf:

Code:

send host-name "<hostname>";
#send dhcp-client-identifier 1:0:a0:24:ab:fb:9c;
#send dhcp-lease-time 3600;
#supersede domain-name "fugue.com home.vix.com";
#prepend domain-name-servers 127.0.0.1;
request subnet-mask, broadcast-address, time-offset, routers,
        domain-name, domain-name-servers, host-name,
        netbios-name-servers, netbios-scope;
#require subnet-mask, domain-name-servers;
timeout 30;
#retry 60;
#reboot 10;
#select-timeout 5;
#initial-interval 2;
#script "/etc/dhcp3/dhclient-script";
#media "-link0 -link1 -link2", "link0 link1";
#reject 192.33.137.209;

#alias {
#  interface "eth0";
#  fixed-address 192.5.5.213;
#  option subnet-mask 255.255.255.255;
#}

#lease {
#  interface "eth0";
#  fixed-address 192.33.137.200;
#  medium "link0 link1";
#  option host-name "andare.swiftmedia.com";
#  option subnet-mask 255.255.255.0;
#  option broadcast-address 192.33.137.255;
#  option routers 192.33.137.250;
#  option domain-name-servers 127.0.0.1;
#  renew 2 2000/1/12 00:00:01;
#  rebind 2 2000/1/12 00:00:01;
#  expire 2 2000/1/12 00:00:01;
#}

I'm using Ubuntu 7.10.

Thank you VERY much in advance,
Nikola

cdbunch · 04-25-2008, 06:16 PM

Based on the information given it seems like the DHCP protocol has reached the phase of the client sending DHCPREQUEST to the DHCP server 10.3.x.x. At that point the server should reply with a DHCPACK and that should conclude the interchange. If the client were to receive and correctly process a DHCPACK from the server then it should stop sending DHCPREQUEST packets.

It would be interesting to see a packet dump of the exchange of DHCP protocol packets to see if possibly the DHCPACK is not being sent or is being blocked somewhere. I cannot see a reason why it would be blocked (for example by a firewall) because the source and destination addresses and ports should be the same for that packet as for the DHCPOFFER packet that the client should have received in order to generate the DHCPREQUEST packets in the first place. This might be influenced by it requesting an IP address from a previous lease.

I think a packet dump would help a lot in figuring out what is going on here.

Cameron Bunch