Short DHCP Lease Times

If you are an Ubuntu user who has experienced WiFi disconnects from public hot spots while other Windows and Mac users around you are Web browsing worry free you're not the only one. In this particular case, however, the fix may be quite easy.

The symptoms my wife experienced were that she could connect to the USC wireless network and happily surf the internet for about an hour before being booted off and not being able to reconnect for a period of about 24-hours. Turns out, according to USC IT department, that defaut DHCP lease time in Ubuntu is shorter than that on Windows and Mac OS. This exceeded whatever arbitrary DHCP renewal rate threshold USC has configured and caused her MAC address to be blacklisted for a day. Here's the fix:

Edit /etc/dhcp3/dhclient.conf as root with the following command (Tip: Use Alt-F2):

gksu gedit /etc/dhcp3/dhclient.conf

Change the DHCP lease time by editing the following option (or adding it if it does not already exist)

option dhcp-lease-time 86399;

That sets the lease time to be 86399 seconds – one second shy of a day.