Lease renewal time

Thu Nov 6 17:06:21 UTC 2014

I have some problems with configuring the isc server on my router. The
lease time was set to 60s (just for tests), after about 30s the dhcp
clients try to renew. Here's the log:

==========CLIENT==========
Nov  6 16:53:15 red-viper dhclient: Internet Systems Consortium DHCP Client 4.3.1
Nov  6 16:53:15 red-viper dhclient: Copyright 2004-2014 Internet Systems Consortium.
Nov  6 16:53:15 red-viper dhclient: All rights reserved.
Nov  6 16:53:15 red-viper dhclient: For info, please visit https://www.isc.org/software/dhcp/
Nov  6 16:53:15 red-viper dhclient:
Nov  6 16:53:15 red-viper dhclient: Listening on LPF/wlan2/e8:de:27:1d:4c:a5
Nov  6 16:53:15 red-viper dhclient: Sending on   LPF/wlan2/e8:de:27:1d:4c:a5
Nov  6 16:53:15 red-viper dhclient: Sending on   Socket/fallback
Nov  6 16:53:15 red-viper dhclient: DHCPDISCOVER on wlan2 to 255.255.255.255 port 67 interval 8
Nov  6 16:53:15 red-viper dhclient: DHCPREQUEST on wlan2 to 255.255.255.255 port 67
Nov  6 16:53:15 red-viper dhclient: DHCPOFFER from 192.168.1.1
Nov  6 16:53:15 red-viper dhclient: DHCPACK from 192.168.1.1
Nov  6 16:53:15 red-viper dhclient: bound to 192.168.1.50 -- renewal in 30 seconds.
==========SERVER==========
Nov  6 16:53:15 the-mountain dhcpd: DHCPDISCOVER from e8:de:27:1d:4c:a5 via br-lan
Nov  6 16:53:15 the-mountain dhcpd: DHCPOFFER on 192.168.1.50 to e8:de:27:1d:4c:a5 via br-lan
Nov  6 16:53:15 the-mountain dhcpd: DHCPREQUEST for 192.168.1.50 (192.168.1.1) from e8:de:27:1d:4c:a5 via br-lan
Nov  6 16:53:15 the-mountain dhcpd: DHCPACK on 192.168.1.50 to e8:de:27:1d:4c:a5 via br-lan
-------------------------------

Everything looks ok.

Now see what happens after the 30secs:

==========CLIENT==========
Nov  6 16:53:45 red-viper dhclient: DHCPREQUEST on wlan2 to 192.168.1.1 port 67
Nov  6 16:53:50 red-viper dhclient: DHCPREQUEST on wlan2 to 192.168.1.1 port 67
Nov  6 16:53:55 red-viper dhclient: DHCPREQUEST on wlan2 to 192.168.1.1 port 67
Nov  6 16:54:09 red-viper dhclient: DHCPREQUEST on wlan2 to 255.255.255.255 port 67
Nov  6 16:54:16 red-viper dhclient: DHCPDISCOVER on wlan2 to 255.255.255.255 port 67 interval 7
Nov  6 16:54:16 red-viper dhclient: DHCPREQUEST on wlan2 to 255.255.255.255 port 67
Nov  6 16:54:16 red-viper dhclient: DHCPOFFER from 192.168.1.1
Nov  6 16:54:16 red-viper dhclient: DHCPACK from 192.168.1.1
Nov  6 16:54:16 red-viper dhclient: bound to 192.168.1.50 -- renewal in 25 seconds.
==========SERVER==========
Nov  6 16:53:45 the-mountain dhcpd: DHCPREQUEST for 192.168.1.50 from e8:de:27:1d:4c:a5 via br-lan
Nov  6 16:53:45 the-mountain dhcpd: DHCPACK on 192.168.1.50 to e8:de:27:1d:4c:a5 via br-lan
Nov  6 16:53:51 the-mountain dhcpd: DHCPREQUEST for 192.168.1.50 from e8:de:27:1d:4c:a5 via br-lan
Nov  6 16:53:51 the-mountain dhcpd: DHCPACK on 192.168.1.50 to e8:de:27:1d:4c:a5 via br-lan
Nov  6 16:53:56 the-mountain dhcpd: DHCPREQUEST for 192.168.1.50 from e8:de:27:1d:4c:a5 via br-lan
Nov  6 16:53:56 the-mountain dhcpd: DHCPACK on 192.168.1.50 to e8:de:27:1d:4c:a5 via br-lan
Nov  6 16:54:10 the-mountain dhcpd: DHCPREQUEST for 192.168.1.50 from e8:de:27:1d:4c:a5 via br-lan
Nov  6 16:54:10 the-mountain dhcpd: DHCPACK on 192.168.1.50 to e8:de:27:1d:4c:a5 via br-lan
Nov  6 16:54:16 the-mountain dhcpd: DHCPDISCOVER from e8:de:27:1d:4c:a5 via br-lan
Nov  6 16:54:16 the-mountain dhcpd: DHCPOFFER on 192.168.1.50 to e8:de:27:1d:4c:a5 via br-lan
Nov  6 16:54:16 the-mountain dhcpd: DHCPREQUEST for 192.168.1.50 (192.168.1.1) from e8:de:27:1d:4c:a5 via br-lan
Nov  6 16:54:16 the-mountain dhcpd: DHCPACK on 192.168.1.50 to e8:de:27:1d:4c:a5 via br-lan
-------------------------------

It tries to get a new lease several times, but something is wrong and
the client doesn't get it. If you check the time, you can say there's
60 seconds between the leases can be obtained.

This happens all the time. Here's another log:

==========CLIENT==========
Nov  6 16:54:41 red-viper dhclient: DHCPREQUEST on wlan2 to 192.168.1.1 port 67
Nov  6 16:54:49 red-viper dhclient: DHCPREQUEST on wlan2 to 192.168.1.1 port 67
Nov  6 16:55:00 red-viper dhclient: DHCPREQUEST on wlan2 to 192.168.1.1 port 67
Nov  6 16:55:12 red-viper dhclient: DHCPREQUEST on wlan2 to 255.255.255.255 port 67
Nov  6 16:55:17 red-viper dhclient: DHCPDISCOVER on wlan2 to 255.255.255.255 port 67 interval 6
Nov  6 16:55:18 red-viper dhclient: DHCPREQUEST on wlan2 to 255.255.255.255 port 67
Nov  6 16:55:18 red-viper dhclient: DHCPOFFER from 192.168.1.1
Nov  6 16:55:18 red-viper dhclient: DHCPACK from 192.168.1.1
Nov  6 16:55:18 red-viper dhclient: bound to 192.168.1.50 -- renewal in 26 seconds.
==========SERVER==========
Nov  6 16:54:41 the-mountain dhcpd: DHCPREQUEST for 192.168.1.50 from e8:de:27:1d:4c:a5 via br-lan
Nov  6 16:54:41 the-mountain dhcpd: DHCPACK on 192.168.1.50 to e8:de:27:1d:4c:a5 via br-lan
Nov  6 16:54:49 the-mountain dhcpd: DHCPREQUEST for 192.168.1.50 from e8:de:27:1d:4c:a5 via br-lan
Nov  6 16:54:49 the-mountain dhcpd: DHCPACK on 192.168.1.50 to e8:de:27:1d:4c:a5 via br-lan
Nov  6 16:55:00 the-mountain dhcpd: DHCPREQUEST for 192.168.1.50 from e8:de:27:1d:4c:a5 via br-lan
Nov  6 16:55:00 the-mountain dhcpd: DHCPACK on 192.168.1.50 to e8:de:27:1d:4c:a5 via br-lan
Nov  6 16:55:12 the-mountain dhcpd: DHCPREQUEST for 192.168.1.50 from e8:de:27:1d:4c:a5 via br-lan
Nov  6 16:55:12 the-mountain dhcpd: DHCPACK on 192.168.1.50 to e8:de:27:1d:4c:a5 via br-lan
Nov  6 16:55:18 the-mountain dhcpd: DHCPDISCOVER from e8:de:27:1d:4c:a5 via br-lan
Nov  6 16:55:18 the-mountain dhcpd: DHCPOFFER on 192.168.1.50 to e8:de:27:1d:4c:a5 via br-lan
Nov  6 16:55:18 the-mountain dhcpd: DHCPREQUEST for 192.168.1.50 (192.168.1.1) from e8:de:27:1d:4c:a5 via br-lan
Nov  6 16:55:18 the-mountain dhcpd: DHCPACK on 192.168.1.50 to e8:de:27:1d:4c:a5 via br-lan

The previous lease was in 16:54:16, and this one is in 16:55:18, so
another minute.

Why does this happen? Shouldn't the client receive the lease when it
want it? I mean, usually clients sets the renewal time to half of the
time specified on the serwer.

I tried to force the clients to have fixed 60s time, and I set the following
options in the server config file:

default-lease-time 60;
min-lease-time 60;
max-lease-time 60;

But nothing seems to work -- the client sets 30s for the renew and has to wait
the other 30s so the lease can expire, and produce the log while they wait.

The version of the server is 4.2.4.

Is there a way to fix this issue?

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