多网段NAT的iptables疑问

Question

最近看到一段多网段NAT的iptables,有几处不解想请教各位，以下是其中几段：

/sbin/iptables -A FORWARD -s 192.168.0.1/255.255.255.0 -j ACCEPT
/sbin/iptables -A FORWARD -s 192.168.1.1/255.255.255.0 -j ACCEPT
/sbin/iptables -A FORWARD -s 192.168.2.1/255.255.255.0 -j ACCEPT
/sbin/iptables -A FORWARD -s 192.168.3.1/255.255.255.0 -j ACCEPT

/sbin/iptables -t nat -A POSTROUTING -o eth2 -s 192.168.0.1/255.255.255.0 -j MASQUERADE
/sbin/iptables -t nat -A POSTROUTING -o eth2 -d 192.168.0.1/255.255.255.0 -j MASQUERADE

/sbin/iptables -t nat -A POSTROUTING -o eth2 -s 192.168.1.1/255.255.255.0 -j MASQUERADE
/sbin/iptables -t nat -A POSTROUTING -o eth2 -d 192.168.1.1/255.255.255.0 -j MASQUERADE

/sbin/iptables -t nat -A POSTROUTING -o eth2 -s 192.168.2.1/255.255.255.0 -j MASQUERADE
/sbin/iptables -t nat -A POSTROUTING -o eth2 -d 192.168.2.1/255.255.255.0 -j MASQUERADE

/sbin/iptables -t nat -A POSTROUTING -o eth2 -s 192.168.3.1/255.255.255.0 -j MASQUERADE
/sbin/iptables -t nat -A POSTROUTING -o eth2 -d 192.168.3.1/255.255.255.0 -j MASQUERADE

/sbin/iptables -t nat -A POSTROUTING -o eth1 -s 192.168.3.1/255.255.255.0 -j MASQUERADE
/sbin/iptables -t nat -A POSTROUTING -o eth1 -d 192.168.3.1/255.255.255.0 -j MASQUERADE

/sbin/iptables -t nat -A POSTROUTING -o eth1 -s 192.168.2.1/255.255.255.0 -j MASQUERADE
/sbin/iptables -t nat -A POSTROUTING -o eth1 -d 192.168.2.1/255.255.255.0 -j MASQUERADE

/sbin/iptables -t nat -A POSTROUTING -o eth1 -s 192.168.1.1/255.255.255.0 -j MASQUERADE
/sbin/iptables -t nat -A POSTROUTING -o eth1 -d 192.168.1.1/255.255.255.0 -j MASQUERADE

/sbin/iptables -t nat -A POSTROUTING -o eth1 -s 192.168.0.1/255.255.255.0 -j MASQUERADE
/sbin/iptables -t nat -A POSTROUTING -o eth1 -d 192.168.0.1/255.255.255.0 -j MASQUERADE

ip route add 192.168.1.0/24 via 192.168.0.1
ip route add 192.168.2.0/24 via 192.168.0.1
ip route add 192.168.3.0/24 via 192.168.0.1

以上几段是否要实现各网段之间互相通信，烦请知者解释一下各段意思。谢谢！

[ 本帖最后由 zfyouyi 于 2006-10-16 14:13 编辑 ]