using non-default MTU for some hosts

[justin at shiningsilence.com]

> Thanks for the prompt response! I was hoping, it would also work the
> other way... Can you give a quick example, please? Let's say, two
> BSD-hosts: "mi" and "pandora" have the jumbo-frame cards and want to use
> them fully. The rest of the network -- say 172.21.128/20 -- can only use
> the 1500-long frames.
>
> What are the commands to enter on both machines? I figure, I must start
> with something like `ifconfig em0 mtu 8000' on each one, but then, how
> do I tell them, that they should limit the mtu to 1500 in almost all
> cases? Thanks again!

You'd probably configure normally with ifconfig, and then use 'route' to
create a static route to "mi" that uses the different MTU size, and then
again for "pandora".  i.e. 1500 is the default, and 8000 is the special
case.  I'm saying this without having tried it, of course.