On Mon, Oct 01, 2012 at 02:40:47AM +0000, James Harper wrote:
I need it the other way around - eth0=1500, eth0.12=9000. I can't
you can't. the MTU of a vlan interface can't be any larger than the MTU of the underlying interface. a plumbing-based analogy is more suited to this situation than the more usual car-based analogy, so here goes: "you can not fit a larger pipe inside a smaller pipe" so, set the eth0 to 9000, eth0.12 to 9000, and make a new vlan interface for everything else with an mtu of 1500.
think of a reason why the hardware MTU couldn't be set to 9000 on the physical interface, but that Linux just doesn't send packets larger than 1500 on eth0.
what? that makes no sense. The MTU setting on an interface is what tells linux how large the packets can be before they have to be fragmented. if you set the MTU to 9000, then you're telling Linux that packets up to that size are OK. it won't magically deduce that you really meant 1500 most of the time but sometimes 9000. craig -- craig sanders <cas@taz.net.au>