Dhcpd won’t let go of old leases

isc-dhcp

We have DHCP setup to hand out leases in the following range:

192.168.10.190 - 192.168.10.254 (roughly 65 leases)

Our small business network only has about 30 computers that use DHCP. We noticed that dhcpd stopped handing out new dynamic leases to the computers, even though there are definitely not 65 computers on the network.

Why has it stopped handing out leases? Is it not releasing old un-used leases? How do we tell dhcpd to let go of old leases and start handing out fresh ones again?

Best Answer

The right option here is to use the one-lease-per-client option. Example:

#
# Sample configuration file for ISC dhcpd for Debian
#
# $Id: dhcpd.conf,v 1.1.1.1 2002/05/21 00:07:44 peloy Exp $
#
ddns-update-style none;
option domain-name "example.net";
option domain-name-servers 1.1.1.1, 2.2.2.2;
option ntp-servers ntp.example.net;

default-lease-time 3600;
max-lease-time 7200;

authoritative;
log-facility local7;
deny declines;
deny duplicates;
one-lease-per-client true;

default-lease-time and max-lease-time have nothing to do with max lease entries(only expiration time of that lease generated at that time). deny duplicates will also enforce that you can't have duplicated lease entries for the same mac but different client identification(a host with dual boot, will probably fail if you boot the secondary OS when still having a valid lease on your primary OS). deny declines will make DHCPDECLINE requests comming from clients to be ignored.

Related Topic