dhclient renewing ip address lesser then 50% of configured lease period

srinirao iamspl_xxx at yahoo.com
Wed Nov 25 04:42:11 UTC 2015


Hello, I have my embedded device running dhclient 3.2.18 release. I have configured the dhcp server lease time as:

max-lease-time    28800;
default-lease-time 7200;
Inspite of configuring default lease time to 2 hours, i get frequent dhcp request going out of my device. The requests go out at a freqnency of 50 minutes every time. I have read in the online documents that DHCP renew request (unicast) can happen after the completion of 50% of lease time configured. But however I find it hard to understand why this (magic number) 50 minutes here.

I am getting very frequent DHCP updates of approximately 50 minutes in /var/log/messages

Nov 10 10:34:05 XXX-XXXX dhclient4: DHCPREQUEST on eth0 to 10.14.176.70 port 67
Nov 10 10:34:05 XXX-XXXX dhclient4: DHCPACK from 10.14.176.70
Nov 10 10:34:06 XXX-XXXX dhclient4: bound to 10.14.180.135 -- renewal in 3240 seconds.
Nov 10 11:28:06 XXX-XXXX dhclient4: DHCPREQUEST on eth0 to 10.14.176.70 port 67
Nov 10 11:28:06 XXX-XXXX dhclient4: DHCPACK from 10.14.176.70
Nov 10 11:28:06 XXX-XXXX dhclient4: bound to 10.14.180.135 -- renewal in 3364 seconds.
Nov 10 12:24:11 XXX-XXXX dhclient4: DHCPREQUEST on eth0 to 10.14.176.70 port 67
Nov 10 12:24:11 XXX-XXXX dhclient4: DHCPACK from 10.14.176.70
Nov 10 12:24:11 XXX-XXXX dhclient4: bound to 10.14.180.135 -- renewal in 3117 seconds.
Nov 10 13:16:08 XXX-XXXX dhclient4: DHCPREQUEST on eth0 to 10.14.176.70 port 67
Nov 10 13:16:08 XXX-XXXX dhclient4: DHCPACK from 10.14.176.70
Nov 10 13:16:09 XXX-XXXX dhclient4: bound to 10.14.180.135 -- renewal in 3127 seconds.
Nov 10 14:08:16 XXX-XXXX dhclient4: DHCPREQUEST on eth0 to 10.14.176.70 port 67
Nov 10 14:08:16 XXX-XXXX dhclient4: DHCPACK from 10.14.176.70
Nov 10 14:08:16 XXX-XXXX dhclient4: bound to 10.14.180.135 -- renewal in 3578 seconds.
Nov 10 15:07:54 XXX-XXXX dhclient4: DHCPREQUEST on eth0 to 10.14.176.70 port 67
Nov 10 15:07:54 XXX-XXXX dhclient4: DHCPACK from 10.14.176.70
Nov 10 15:07:55 XXX-XXXX dhclient4: bound to 10.14.180.135 -- renewal in 2843 seconds.
Nov 10 15:55:19 XXX-XXXX dhclient4: DHCPREQUEST on eth0 to 10.14.176.70 port 67
Nov 10 15:55:19 XXX-XXXX dhclient4: DHCPACK from 10.14.176.70
Nov 10 15:55:19 XXX-XXXX dhclient4: bound to 10.14.180.135 -- renewal in 3206 seconds.
Nov 10 16:48:45 XXX-XXXX dhclient4: DHCPREQUEST on eth0 to 10.14.176.70 port 67
Nov 10 16:48:45 XXX-XXXX dhclient4: DHCPACK from 10.14.176.70
Nov 10 16:48:45 XXX-XXXX dhclient4: bound to 10.14.180.135 -- renewal in 3001 seconds.
Nov 10 17:38:46 XXX-XXXX dhclient4: DHCPREQUEST on eth0 to 10.14.176.70 port 67
Nov 10 17:38:46 XXX-XXXX dhclient4: DHCPACK from 10.14.176.70
Nov 10 17:38:46 XXX-XXXX dhclient4: bound to 10.14.180.135 -- renewal in 3227 seconds.
Nov 10 18:32:33 XXX-XXXX dhclient4: DHCPREQUEST on eth0 to 10.14.176.70 port 67
Nov 10 18:32:33 XXX-XXXX dhclient4: DHCPACK from 10.14.176.70
Nov 10 18:32:33 XXX-XXXX dhclient4: bound to 10.14.180.135 -- renewal in 3247 seconds.
Nov 10 19:26:41 XXX-XXXX dhclient4: DHCPREQUEST on eth0 to 10.14.176.70 port 67
Nov 10 19:26:41 XXX-XXXX dhclient4: DHCPACK from 10.14.176.70
Nov 10 19:26:41 XXX-XXXX dhclient4: bound to 10.14.180.135 -- renewal in 3512 seconds.
Nov 10 20:25:13 XXX-XXXX dhclient4: DHCPREQUEST on eth0 to 10.14.176.70 port 67
Nov 10 20:25:13 XXX-XXXX dhclient4: DHCPACK from 10.14.176.70
Nov 10 20:25:14 XXX-XXXX dhclient4: bound to 10.14.180.135 -- renewal in 2853 seconds.
Nov 10 21:12:47 XXX-XXXX dhclient4: DHCPREQUEST on eth0 to 10.14.176.70 port 67
Nov 10 21:12:47 XXX-XXXX dhclient4: DHCPACK from 10.14.176.70
Nov 10 21:12:47 XXX-XXXX dhclient4: bound to 10.14.180.135 -- renewal in 3146 seconds.
Nov 10 22:05:13 XXX-XXXX dhclient4: DHCPREQUEST on eth0 to 10.14.176.70 port 67
Nov 10 22:05:13 XXX-XXXX dhclient4: DHCPACK from 10.14.176.70
Nov 10 22:05:13 XXX-XXXX dhclient4: bound to 10.14.180.135 -- renewal in 2776 seconds.
Nov 10 22:51:29 XXX-XXXX dhclient4: DHCPREQUEST on eth0 to 10.14.176.70 port 67
Nov 10 22:51:29 XXX-XXXX dhclient4: DHCPACK from 10.14.176.70
Nov 10 22:51:30 XXX-XXXX dhclient4: bound to 10.14.180.135 -- renewal in 3359 seconds.
Nov 10 23:47:29 XXX-XXXX dhclient4: DHCPREQUEST on eth0 to 10.14.176.70 port 67
Nov 10 23:47:29 XXX-XXXX dhclient4: DHCPACK from 10.14.176.70
Nov 10 23:47:29 XXX-XXXX dhclient4: bound to 10.14.180.135 -- renewal in 3039 seconds.
Nov 11 00:38:08 XXX-XXXX dhclient4: DHCPREQUEST on eth0 to 10.14.176.70 port 67
Nov 11 00:38:08 XXX-XXXX dhclient4: DHCPACK from 10.14.176.70
Nov 11 00:38:08 XXX-XXXX dhclient4: bound to 10.14.180.135 -- renewal in 2998 seconds.
Nov 11 01:28:07 XXX-XXXX dhclient4: DHCPREQUEST on eth0 to 10.14.176.70 port 67
Nov 11 01:28:07 XXX-XXXX dhclient4: DHCPACK from 10.14.176.70
Nov 11 01:28:07 XXX-XXXX dhclient4: bound to 10.14.180.135 -- renewal in 3200 seconds.
Nov 11 02:21:28 XXX-XXXX dhclient4: DHCPREQUEST on eth0 to 10.14.176.70 port 67
Nov 11 02:21:28 XXX-XXXX dhclient4: DHCPACK from 10.14.176.70
Nov 11 02:21:28 XXX-XXXX dhclient4: bound to 10.14.180.135 -- renewal in 2866 seconds.
Nov 11 03:09:15 XXX-XXXX dhclient4: DHCPREQUEST on eth0 to 10.14.176.70 port 67
Nov 11 03:09:15 XXX-XXXX dhclient4: DHCPACK from 10.14.176.70
Nov 11 03:09:15 XXX-XXXX dhclient4: bound to 10.14.180.135 -- renewal in 3378 seconds.
Nov 11 04:05:33 XXX-XXXX dhclient4: DHCPREQUEST on eth0 to 10.14.176.70 port 67
Nov 11 04:05:33 XXX-XXXX dhclient4: DHCPACK from 10.14.176.70
Nov 11 04:05:33 XXX-XXXX dhclient4: bound to 10.14.180.135 -- renewal in 3580 seconds.
Nov 11 05:05:13 XXX-XXXX dhclient4: DHCPREQUEST on eth0 to 10.14.176.70 port 67
Nov 11 05:05:14 XXX-XXXX dhclient4: DHCPACK from 10.14.176.70
Nov 11 05:05:14 XXX-XXXX dhclient4: bound to 10.14.180.135 -- renewal in 3539 seconds.
Nov 11 06:04:13 XXX-XXXX dhclient4: DHCPREQUEST on eth0 to 10.14.176.70 port 67
Nov 11 06:04:13 XXX-XXXX dhclient4: DHCPACK from 10.14.176.70
Nov 11 06:04:13 XXX-XXXX dhclient4: bound to 10.14.180.135 -- renewal in 2772 seconds.
Nov 11 06:50:25 XXX-XXXX dhclient4: DHCPREQUEST on eth0 to 10.14.176.70 port 67
Nov 11 06:50:25 XXX-XXXX dhclient4: DHCPACK from 10.14.176.70
Nov 11 06:50:26 XXX-XXXX dhclient4: bound to 10.14.180.135 -- renewal in 3126 seconds.
Nov 11 07:42:32 XXX-XXXX dhclient4: DHCPREQUEST on eth0 to 10.14.176.70 port 67
Nov 11 07:42:32 XXX-XXXX dhclient4: DHCPACK from 10.14.176.70
Nov 11 07:42:32 XXX-XXXX dhclient4: bound to 10.14.180.135 -- renewal in 3087 seconds.
Nov 11 08:33:59 XXX-XXXX dhclient4: DHCPREQUEST on eth0 to 10.14.176.70 port 67
Nov 11 08:33:59 XXX-XXXX dhclient4: DHCPACK from 10.14.176.70
Nov 11 08:33:59 XXX-XXXX dhclient4: bound to 10.14.180.135 -- renewal in 2779 seconds.
and so on.My DHCP client configuration file only has following options enabled:

request subnet-mask, broadcast-address, time-offset, routers,
domain-name, domain-name-servers, host-name,
netbios-name-servers, netbios-scope;

And my lease file logs these responses (approximately every 50 minutes) as :lease {
  interface "eth0";
  fixed-address 10.14.180.135;
  option subnet-mask 255.255.255.128;
  option routers 10.14.180.129;
  option dhcp-lease-time 7200;
  option dhcp-message-type 5;
  option domain-name-servers 10.14.176.70,10.14.176.2;
  option dhcp-server-identifier 10.14.176.70;
  option domain-name "b08.okc.mydomain.com.";
  renew 3 2015/11/18 05:37:22;
  rebind 3 2015/11/18 06:26:23;
  expire 3 2015/11/18 06:41:23;
}
lease {
  interface "eth0";
  fixed-address 10.14.180.135;
  option subnet-mask 255.255.255.128;
  option routers 10.14.180.129;
  option dhcp-lease-time 7200;
  option dhcp-message-type 5;
  option domain-name-servers 10.14.176.70,10.14.176.2;
  option dhcp-server-identifier 10.14.176.70;
  option domain-name "b08.okc.mydomain.com.";
  renew 3 2015/11/18 06:28:43;
  rebind 3 2015/11/18 07:22:22;
  expire 3 2015/11/18 07:37:22;
}
lease {
  interface "eth0";
  fixed-address 10.14.180.135;
  option subnet-mask 255.255.255.128;
  option routers 10.14.180.129;
  option dhcp-lease-time 7200;
  option dhcp-message-type 5;
  option domain-name-servers 10.14.176.70,10.14.176.2;
  option dhcp-server-identifier 10.14.176.70;
  option domain-name "b08.okc.mydomain.com.";
  renew 3 2015/11/18 07:14:31;
  rebind 3 2015/11/18 08:13:43;
  expire 3 2015/11/18 08:28:43;
}
lease {
  interface "eth0";
  fixed-address 10.14.180.135;
  option subnet-mask 255.255.255.128;
  option routers 10.14.180.129;
  option dhcp-lease-time 7200;
  option dhcp-message-type 5;
  option domain-name-servers 10.14.176.70,10.14.176.2;
  option dhcp-server-identifier 10.14.176.70;
  option domain-name "b08.okc.mydomain.com.";
  renew 3 2015/11/18 08:01:46;
  rebind 3 2015/11/18 08:59:31;
  expire 3 2015/11/18 09:14:31;
}
lease {
  interface "eth0";
  fixed-address 10.14.180.135;
  option subnet-mask 255.255.255.128;
  option routers 10.14.180.129;
  option dhcp-lease-time 7200;
  option dhcp-message-type 5;
  option domain-name-servers 10.14.176.70,10.14.176.2;
  option dhcp-server-identifier 10.14.176.70;
  option domain-name "b08.okc.mydomain.com.";
  renew 3 2015/11/18 08:57:34;
  rebind 3 2015/11/18 09:46:46;
  expire 3 2015/11/18 10:01:46;
}
lease {
  interface "eth0";
  fixed-address 10.14.180.135;
  option subnet-mask 255.255.255.128;
  option routers 10.14.180.129;
  option dhcp-lease-time 7200;
  option dhcp-message-type 5;
  option domain-name-servers 10.14.176.70,10.14.176.2;
  option dhcp-server-identifier 10.14.176.70;
  option domain-name "b08.okc.mydomain.com.";
  renew 3 2015/11/18 09:51:31;
  rebind 3 2015/11/18 10:42:34;
  expire 3 2015/11/18 10:57:34;
}
and so on. 

What could I be doing wrong? According to me, the ip address should not need to change that often. 

Please helpsrini rao

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