June 12, 2014 by Rishit Patel
I recently worked on an Infoblox DHCP project and found DHCP lease logging useful in understanding DHCP operations within a customer network and helpful in troubleshooting client DHCP services. I’ve shared some useful information in this blog for everyone to understand the advantages of DHCP lease logging over DHCP messages in syslog.
When you enable DHCP lease logging, detailed DHCP lease history is maintained in a separate 100,000 maximum entry database on a designated Grid Member. The advantage of having lease logging enabled is that only DHCP lease events are logged which include additional lease specific details not included in a syslog output which are formatted nicely for the end-user and retained in a separate lease database on the specified logging member. Search capabilities are also included, which are crucial for security auditing and for meeting new compliance regulations such as SOX and HIPAA.
Best practice when enabling lease logging:
1. The lease logging member should NOT be the Grid Master or DHCP server
2. If all members are DHCP servers, best to select the least used of those members (other than the Grid Master).
One thing to note is that the lease log can only contain 100,000 records and once the database reaches 100,000 entries it will automatically maintain this limit entries by rolling off the oldest records as new ones come in.
DHCP lease information is also available in Syslog but with much less detail which is combined with DNS and other system related messages. The primary benefit of syslog is that it can store records much longer and keeps the last 10 syslog files compressed for extraction purposes to search at a later date if necessary.
To specify lease logging for a member:
1. From the Data Management tab, select the DHCP tab -> Members tab -> Members -> member check box, and then click the Edit icon.
2. In the Logging tab, Lease Logging: Select Log Lease Events from DHCP Server to enable DHCP lease logging.
3. To disable DHCP lease logging, clear the check box.
4. You can set member overrides if you want to enable or disable lease logging per member.
5. Send leases to: In the Select Member dialog box, select the Grid member on which you want to store the DHCP lease history log.
6. Save the configuration and click Restart if it appears at the top of the screen.
