Tracking ACKed leases (mac to IP) in realtime?

Jason Antman jantman at
Thu Sep 8 19:51:33 UTC 2011

We're running dhcpd 4.2.0 on CentOS 5.5, primarily backing a number of 
wireless networks (a bunch of /20s and a few /19s... up to about 20k 
leases at a time, all with 1800 second leases. We're using a large 
amount of L2 wireless equipment, which (long story short) only logs a 
username to a MAC address. In order to support services that require 
quickly mapping a username to an IP (wireless printing, among others), 
we've been running rsyslog to parse the DHCPACK log messages into MySQL, 
and keep a table of real-time MAC to IP pairings.

I was wondering what other solutions people are using to do this? Up 
until a year or two ago we used a script to parse the leases file 
(triggered via cron every few minutes), but since we started allowing 
students to do wireless printing in our labs, we've needed near-realtime 
parsing to keep up with user expectations.

I know there was discussion a while back of a MySQL-based (or dbi-based) 
lease storage patch, but if memory serves it either never got off the 
ground or never made it to production quality.

Classes started this week, and so far I've been seeing somewhere on the 
order of up to 70 syslog messages per second, which has hit our 
rsyslog-to-mysql code pretty hard.

Thanks for any advice/input,
Jason Antman
Rutgers University


Jason Antman
System Administrator
Rutgers University
OIT Central Systems & Services / NetOps

Office: 732-445-6363
Cell: 732-983-7256
jantman at

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