Strange behaviour from dhcp server

[Tobias Szyndler]

Hello list

my first post, so hopefully I do not ask something obvious :-)
We have a strange problem with one of our dhcp servers. The problem is 
that the server offers an IP to the client via DHCPOFFER but in the 
following DHCPREQUEST from the client the server returns 'unknown lease'.
After some of these 'unknown lease' the client comes again with 
DHCPDISCOVER and this time the server offers another IP which seems to 
work for the server and after the DHCPREQUEST from the client for that 
IP the server sends the expected DHCPACK
I put some of the loglines here (ip addresses anonymized):
<<
Sep  7 09:12:14 dhcp1 dhcpd: DHCPDISCOVER from 00:0f:93:00:10:ba via x.y.z.1
Sep  7 09:12:23 dhcp1 dhcpd: DHCPDISCOVER from 00:0f:93:00:10:ba via x.y.z.1
Sep  7 09:12:24 dhcp1 dhcpd: DHCPOFFER on x.y.z.112 to 00:0f:93:00:10:ba 
via x.y.z.1
Sep  7 09:12:24 dhcp1 dhcpd: DHCPREQUEST for x.y.z.112 (x.y.z.1) from 
00:0f:93:00:10:ba via x.y.z.1: unknown lease x.y.z.112.
Sep  7 09:12:25 dhcp1 dhcpd: DHCPREQUEST for x.y.z.112 (x.y.z.1) from 
00:0f:93:00:10:ba via x.y.z.1: unknown lease x.y.z.112.
Sep  7 09:12:27 dhcp1 dhcpd: DHCPREQUEST for x.y.z.112 (x.y.z.1) from 
00:0f:93:00:10:ba via x.y.z.1: unknown lease x.y.z.112.
Sep  7 09:12:27 dhcp1 dhcpd: DHCPDISCOVER from 00:0f:93:00:10:ba via x.y.z.1
Sep  7 09:12:27 dhcp1 dhcpd: DHCPOFFER on x.y.z.112 to 00:0f:93:00:10:ba 
via x.y.z.1
Sep  7 09:12:27 dhcp1 dhcpd: DHCPREQUEST for x.y.z.112 (x.y.z.1) from 
00:0f:93:00:10:ba via x.y.z.1: unknown lease x.y.z.112.
Sep  7 09:12:28 dhcp1 dhcpd: DHCPREQUEST for x.y.z.112 (x.y.z.1) from 
00:0f:93:00:10:ba via x.y.z.1: unknown lease x.y.z.112.
Sep  7 09:12:30 dhcp1 dhcpd: DHCPREQUEST for x.y.z.112 (x.y.z.1) from 
00:0f:93:00:10:ba via x.y.z.1: unknown lease x.y.z.112.
Sep  7 09:12:33 dhcp1 dhcpd: DHCPREQUEST for x.y.z.112 (x.y.z.1) from 
00:0f:93:00:10:ba via x.y.z.1: unknown lease x.y.z.112.
Sep  7 09:12:37 dhcp1 dhcpd: DHCPREQUEST for x.y.z.112 (x.y.z.1) from 
00:0f:93:00:10:ba via x.y.z.1: unknown lease x.y.z.112.
Sep  7 09:12:41 dhcp1 dhcpd: DHCPREQUEST for x.y.z.112 (x.y.z.1) from 
00:0f:93:00:10:ba via x.y.z.1: unknown lease x.y.z.112.
<<here the dhcp server restarts>>
Sep  7 09:14:10 dhcp1 dhcpd: DHCPDISCOVER from 00:0f:93:00:10:ba via x.y.z.1
Sep  7 09:14:11 dhcp1 dhcpd: DHCPOFFER on x.y.z.221 to 00:0f:93:00:10:ba 
via x.y.z.1
Sep  7 09:14:11 dhcp1 dhcpd: DHCPREQUEST for x.y.z.221 (x.y.z.1) from 
00:0f:93:00:10:ba via x.y.z.1
Sep  7 09:14:11 dhcp1 dhcpd: DHCPACK on x.y.z.221 to 00:0f:93:00:10:ba 
via x.y.z.1
 >>
I really do not understand why the server first offers an IP which it 
does not allow in the following DHCPREQUEST by the client. For me it 
sounds odd that the server tries to offer the 112 IP several times and 
then suddenly (after dhcp restart) offers 221 and everything works

Does anyone have an idea where we could check more to narrow down this 
problem?

Furthermore I wonder if there is a config setting in dhcpd.conf to force 
the dhcp to only give one IP per mac address. Sometimes we have the case 
that the same MAC seems to receive more than one IP.

Thanks a lot for any hint and have a nice weekend

tobi