split на bash'і

snat=(
    55410:192.168.10.99:80
    55415:192.168.10.199:80
    55411:192.168.20.99:80
    55412:192.168.30.199:80
    55413:192.168.24.99:80
    55414:192.168.20.199:80
)

for i in ${snat[@]}; do
    set -- "$i"
    IFS=":"; declare -a Array=($*)

    iptables -A FORWARD -p tcp -s ${Array[1]} --sport ${Array[2]} -j ACCEPT
    iptables -A FORWARD -p tcp -d ${Array[1]} --dport ${Array[2]} -j ACCEPT
    iptables -t nat -A PREROUTING -p tcp -i eth0 --dport ${Array[0]} -j DNAT --to-destination ${Array[1]}\:${Array[2]}

    echo "${Array[@]}"
done

п.с. збоченська мова