I appreciate the great suggestions on this one. The net result of all still ends up being that once the ":" and "," that are part of the '-N addr1:remapaddr1,addr2:remapaddr2' arg to tcpreplay, are passed thru, they end up looking like this to tcpreplay:

'-N addr1 remapaddr1 addr2 remapaddr2'

which is of course, wrong as far as it's concerned.

I appreciate the thoughts - if I solve this, I will post the result. If anyone else gets it to work, I'd love to see how.

Thanks! - bill