I've discovered that this is actually a bug (or badly designed "feature") in the isc-dhcp package.
I upstreamed the bug here: https://bugs.launchpad.net/ubuntu/+source /isc-dhcp/+bug/1524093 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1442837 Title: "ifdown wlan0" brings down multiple interfaces, not just the specified one To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ifupdown/+bug/1442837/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
