wip: support for external zone
external zone support
$ ./network-split.sh -d setup ax
ZONE_A="192.168.1.229"
ZONE_B="10.1.160.127 10.1.160.158 10.1.160.160 10.1.160.163"
ZONE_C="10.1.160.103 10.1.160.162 10.1.160.65 10.1.160.98"
ZONE_X="77.75.75.172"
current zone: ZONE_A
ax: ZONE_X will be blocked from ZONE_A
iptables -A INPUT -s 77.75.75.172 -j DROP -v
iptables -A OUTPUT -d 77.75.75.172 -j DROP -v