[Simh] Any experience with tun/tap or bpf?

[Galen Tackett]

I've been thinking about setting up a link between my SimH VAX 
environment and the host Mac OS X system using either the tun/tap 
package (already installed by me) or the bpf device (part of OS X). But 
from what I've read so far I haven't been able to figure out how to set 
either of them up. (I do have the emulated DEQNA working already and 
can run IP on it.)

I'm a long term veteran of VMS and general networking technology but am 
still a bit of a beginner with the Unix side of things, whether under 
OS X or elsewhere.

Can anyone offer a few tips of  how to set things up for either tun/tap 
or bpf?