Is it normal for start time to be later than end time in the leases file?

[David Coulthart]

I'm running a pair of DHCP servers (3.0.4, working to upgrade to  
3.1.1) with failover configured.  I received a report that a host that  
is configured with a fixed address was having trouble obtaining its  
lease.  It was previously receiving an IP from the dynamic pool for  
the same network.  The messages in the logs were:

Aug 20 10:12:38 <primary-dhcp-server> dhcpd: [ID 702911 local6.info]  
DHCPDISCOVER from <MAC> via <gateway IP>
Aug 20 10:12:38 <primary-dhcp-server> dhcpd: [ID 702911 local6.info]  
DHCPOFFER on <fixed-IP> to <MAC> via <gateway IP>
Aug 20 10:12:38 <secondary-dhcp-server> dhcpd: [ID 702911  
local6.error] uid lease <dynamic-IP> for client <MAC> is duplicate on  
<shared-network>
Aug 20 10:12:38 <secondary-dhcp-server> dhcpd: [ID 702911 local6.info]  
DHCPDISCOVER from <MAC> via <gateway IP>
Aug 20 10:12:38 <secondary-dhcp-server> dhcpd: [ID 702911 local6.info]  
DHCPOFFER on <fixed-IP> to <MAC> via <gateway IP>
Aug 20 10:12:38 <primary-dhcp-server> dhcpd: [ID 702911 local6.info]  
DHCPREQUEST for <fixed-IP> (<secondary-dhcp-server-IP>) from <MAC> via  
<gateway IP>
Aug 20 10:12:38 <primary-dhcp-server> dhcpd: [ID 702911 local6.info]  
DHCPACK on <fixed-IP> to <MAC> via <gateway IP>
Aug 20 10:12:38 <primary-dhcp-server> dhcpd: [ID 702911 local6.info]  
DHCPREQUEST for <fixed-IP> (<secondary-dhcp-server-IP>) from <MAC> via  
<gateway IP>
Aug 20 10:12:38 <secondary-dhcp-server> dhcpd: [ID 702911  
local6.error] uid lease <dynamic-IP> for client <MAC> is duplicate on  
<shared-network>
Aug 20 10:12:38 <secondary-dhcp-server> dhcpd: [ID 702911 local6.info]  
DHCPREQUEST for <fixed-IP> (<secondary-dhcp-server-IP>) from <MAC> via  
<gateway IP>
Aug 20 10:12:38 <primary-dhcp-server> dhcpd: [ID 702911 local6.info]  
DHCPACK on <fixed-IP> to <MAC> via <gateway IP>
Aug 20 10:12:38 <secondary-dhcp-server> dhcpd: [ID 702911 local6.info]  
DHCPACK on <fixed-IP> to <MAC> via <gateway IP>
Aug 20 10:12:38 <secondary-dhcp-server> dhcpd: [ID 702911  
local6.error] uid lease <dynamic-IP> for client <MAC> is duplicate on  
<shared-network>
Aug 20 10:12:38 <secondary-dhcp-server> dhcpd: [ID 702911 local6.info]  
DHCPREQUEST for <fixed-IP> (<secondary-dhcp-server-IP>) from <MAC> via  
<gateway IP>
Aug 20 10:12:38 <secondary-dhcp-server> dhcpd: [ID 702911 local6.info]  
DHCPACK on <fixed-IP> to <MAC> via <gateway IP>

Examining the leases files for the MAC address in question, I found:

On the secondary DHCP server:

lease <dynamic-IP> {
   starts 2 2008/08/19 05:35:52;
   ends 5 2008/08/15 16:26:53;
   tstp 5 2008/08/15 16:26:53;
   tsfp 2 2008/08/19 05:35:52;
   atsfp 2 2008/08/19 05:35:52;
   cltt 5 2008/08/15 16:24:50;
   binding state backup;
   hardware ethernet <MAC>;
   uid "<UID>";
}

lease <dynamic-IP-#2-in-same-shared-network> {
   starts 2 2008/08/19 07:51:03;
   ends 6 2008/08/16 04:56:25;
   tstp 6 2008/08/16 04:56:25;
   tsfp 2 2008/08/19 07:51:03;
   atsfp 2 2008/08/19 07:51:03;
   cltt 5 2008/08/15 16:56:53;
   binding state backup;
   hardware ethernet <MAC>;
   uid "<UID>";
}


On the primary DHCP server:

lease <dynamic-IP> {
   starts 2 2008/08/19 05:35:52;
   ends 5 2008/08/15 16:26:53;
   tstp 2 2008/08/19 05:35:52;
   tsfp 2 2008/08/19 05:35:52;
   atsfp 2 2008/08/19 05:35:52;
   cltt 5 2008/08/15 16:24:50;
   binding state backup;
   hardware ethernet <MAC>;
   uid "<UID>";
}

lease <dynamic-IP-#2-in-same-shared-network> {
   starts 2 2008/08/19 07:51:03;
   ends 6 2008/08/16 04:56:25;
   tstp 2 2008/08/19 07:51:03;
   tsfp 2 2008/08/19 07:51:03;
   atsfp 2 2008/08/19 07:51:03;
   cltt 5 2008/08/15 16:56:53;
   binding state backup;
   hardware ethernet <MAC>;
   uid "<UID>";
}


The part that stymied me was that the date listed for "ends" was  
earlier than the date listed for "starts".  I cooked up a small perl  
script to do a quick check & found that approximately 32,000 out of  
81,000 leases exhibited this phenomenon.  Is this normal?  I fed these  
configs & leases files to dhcpd 3.1.1 using the -t & -T options and  
didn't receive any warnings.

Thx,
Dave Coulthart