interface bonding

[John]

Is there any way to bond sniffer interfaces?
I've read a little on netgraph and it seems 
like i maybe able to use that but i'm not sure 
how to go about that.
 
Basicly the end result is to have snort listen on
a virtual interface, which will have data sent to
it from say fxp0 and fxp1. I also want to make sure that
data from fxp0, fxp1 or $VIRTUAL doesn't get sent out 
fxp1 or fxp0 for some reason.