In my testing on Xenial, you cannot set a child interface MTU to a value greater than its parent. For example, if eth0's MTU is 1500, setting eth0.100's MTU to 9000 (or 1501) causes:
SIOCSIFMTU: Numerical result out of range This restriction makes sense when you consider the physical topology, since packets from eth0.100 would be sent via eth0. If the system attempts to send a packet larger than 1500 bytes via eth0 in this case, it would be dropped. This issue makes me wish it were possible to set a "L3 MTU" (i.e., one that would be the default PMTU MSS, and fragment threshold for other packet types such as UDP and ICMP). -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1565804 Title: ifup of vlan interfaces failing during networking start - RTNETLINK answers: File exists To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ifupdown/+bug/1565804/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
