This is still an issue in Ubuntu 16.04 up to the current date. It is an interface bug, as Robin Sheat pointed out.
-- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to network-manager in Ubuntu. https://bugs.launchpad.net/bugs/269910 Title: Netmask automatically changes to 24 Status in network-manager package in Ubuntu: Fix Released Bug description: Binary package hint: network-manager I have added a new wireless connection with a WPA2 password and a manual IP address, like this: IP address: 126.96.36.199, Netmask: 255.255.255.0 Gateway: 188.8.131.52 I also added two DNS servers. The connection is flawless (pass my compliments to whoever responsible for this, I could never get it to work on Hardy). However, when I edit the wireless connection again, for some reason, the Netmask changes to 24. Just 24. The connection still works. Everything else is the same. network-manager version: 0.7~~svn20080908t183521+eni0-0ubuntu2 I'm running Ubuntu Intrepid Ibex Alpha 5. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/network-manager/+bug/269910/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : email@example.com Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp