Looking over this:

http://wiki.mikrotik.com/wiki/Manual:Ma ... uterBoards

I see that the three ports that come with the RB600 all support some manner of "jumbo" ethernet frames.

I have an RB600 with a daughter board and was wondering if the support for "jumbo" frames extended to these on the RB600?

I'm going to take a wild stab in the dark and guess "no" (based on the hardware support for "jumbo" frames across the routerboard line.

...but now I'm curious to know what the jumbo frame support is like for the x86 platform.

Thanks in advance for any light that can be shown on this subject.

The daughter boards are only 100BaseT, so they shouldn't support Jumbo Frames. But the onboard gigabit ports do support Jumbo Frames.

exactly, jumbo frame support is per interface hardware. Ports on daughterboard do not share same ports as RB600 itself.

About x86 cards - you should look at each interface specification on what it supports or does not support.