Reading many comments about vtun available through google searchs seems 
to imply it supports IPv6.
When I install it (v 3.0.2-1) and bind it to an interface that does NOT 
have IPv4 defined (only v6), start the service, and do a 'netstat 
-nat|grep 5000', I see it bound to 0.0.0.0:5000, not to the IPv6 0::/128 
equiv address.
What gives?  IPv6 support or not?
Meanwhile I found the kame vtun:  
http://orange.kame.net/dev/cvsweb.cgi/v6tun/?cvsroot=apps
And was given the following 'changes' to compile it on linux.  Do I need
this???
v6tun: v6tun.o
        gcc v6tun.c v6tun.h -o v6tun
install: v6tun
        -rm -f $(install_dir)/v6tun
        install -c -o root -g wheel -m 04710 v6tun $(install_dir)
clean: 6tun: v6tun.o    -rm -f *.o v6tun
        gcc v6tun.c v6tun.h -o v6tun install: v6tun
        -rm -f $(install_dir)/v6tun
        install -c -o root -g wheel -m 04710 v6tun $(install_dir) clean:
        -rm -f *.o v6tun