Probably the same issue as bug #61989. If it is, removing "interface- mtu" from request-line in /etc/dhcp3/dhclient.conf and rebooting will fix it.
-- Major Problem with DHCP setting MTU Correctly. https://launchpad.net/bugs/65787 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
