dhcpd.leases file does not get updated

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Environment

SUSE Linux Enterprise Server 11 Service Pack 1

Situation

On a number of DHCP servers at a customer site it was observed that the /var/lib/dhcp/db/dhcpd.leases file did not get updated, despite the fact that clients did get addresses from the server upon request.

Resolution

Investigation revealed a common denominator for all the IP addresses assignments, which were not recorded in dhcpd.leases. Each of them was defined in a fixed-address statement in /etc/dhcpd.conf.
The lease file is not used when handing out addresses that are fixed.

Fixed-address assignments are not considered leases by dhcpd and thus they are not recorded in dhcpd.leases. To the client it looks like a "normal" lease is allocated, but on the server the fixed-address clients go through a completely different code path. They do not go through the same lease allocation routines, so the lease is not recorded in dhcpd.leases. The ISC dhcpd has always worked like this.

Additional Information

To verify this, perform a DHCP request from client with an undefined MAC address that is connected to network served by the DHCP server. The lease information should then appear in dhcpd.leases (given of course a range has been configured).

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