Rebuilding Leases file from log file

Larry Apolonio isc-dhcp at
Tue Nov 27 20:57:39 UTC 2007

I know its not perfect but is it possible to send dhcp logs to a remote 
syslog server and rebuild the dhcp leases file based on mac, IP address 
was assigned, and time. I'd use the lease time in dhcpd.conf to 
configure the amount of time.  Say the lease time was 1 day then

Nov  9 12:24:32 dhcp-server dhcpd: DHCPACK on to 
00:00:00:00:22:95 via

would become

lease {
  starts 2 2007/11/09 12:24:32;
  ends 4 2007/11/11 12:24:32;
  tstp 4 2007/11/11 12:24:32;
  binding state free;
  hardware ethernet 00:00:00:00:22:95;

What bad mojo would I encounter?

Basically would I be able to start up my spare server as the DHCP server 
with the dhcpd.conf file using a leases file generated from the syslog 

Now I can put the leases file in tmpfs or /dev/ram, syslog would be off 
the DHCP server, and we would be using something more current than an 
hourly rsync of the leases file.

Larry Apolonio

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