Help Windows! My DHCP scope is full!

Start of new semester at the U… it seems everyone came back with more WiFi gadgets than ever, and wants them all on the network AT ONCE.  So, our /20 network (4096 addresses) we already planned to supplant with another /22 (1024) but those both filled-up on day one.  Drop the 1 hour DHCP lease to 30 minutes!  Hey, that’s not helping!

Windows 2003 had a registry entry for “LeaseExtension”  (HKLM\System\CurrentControlSet\Services\DHCPServer\ Parameters\LeaseExtension) that defaulted to FOUR (as in ONE-TWO-THREE-HOLY HECK WHEN CAN WE REUSE THIS IP-FOUR) hours.  In addition, the CleanupInterval is 60 minutes (unless the scope is FULL – old/unused IPs are only cleaned once an hour).  So… 30 minutes + 4 HOURS + up to 60 more minutes = 5.5 hours a client uses our Windows 2008R2 DHCP server’s address.

Drop LeaseExtension down, drop down the CleanupInterval – things are more sane (until we finish a re-IP project and take over a second and maybe third /20 for central-campus WiFi).

Thanks goes out to Mike Perth for the first+best Google answer to our issue.

This entry was posted in Uncategorized. Bookmark the permalink.

Leave a Reply