Wow, thanks for the help
This is the switch, that never seem to arrive
http://kbserver.netgear.com/products/GS108T.asp
The BSD-machine only got 100Mb so from what I've heard you cant set jumboframes on it (that is you cant change MTU upwards much at all I guess). Will very likely have it on its own routerinterface or VLAN so the jumboframes will be repackaged in the router anyway.
I tried running that command in Vista, but it gave me two outputs (one with MTU 1500 and another with MTU something very very large. Didn't say if my regular interface (the 1500 one) was subinterface 0 or 1 or 2, so feels scary changing MTU of subinterface 1 without knowing what interface that is.....I'll google some on it, might be able to set it within the registry or something, or just change it in gui to 7000K and then go check if it did set it to 7000 or 7x1024
One of my XP-machines only have Enable/Disable too choose for Jumbo Frames, so there indeed I have to set the MTU through CMD/Registry/whatever google will tell me.