How to tell if IFS file is on NFS

I have been trying to put something together to analyze disk space usage in the 
IFS root file system. I found the IBM IFS tools, and the QRYIFSLIB is pretty 
close to what I want, but I need to fix it up a bit. One problem is that we 
have a number of NFS mounts, and rather than exclude them explicitly (which 
means I would have to know what they are at all times, which I don't) I would 
prefer to add a switch to make the utility ignore them automatically.

The QRYIFSLIB utility is built aroud lstat. lstat has a couple fields that look 
like they might be useful, such as st_dev and st_rdev, but I haven't found 
enough doc to really tell me what they do.

Anybody know of something in stat/lstat that would tell me a file is remote? 
WRKLNK opt 8 displays Remote or Local for "System object is on", so I know the 
info is available, I just don't know where to get it.

Thanks,
-Marty