配置iptables防火牆（二）
DNAT策略的應用
1、清空所有表的防火牆
[root@s2 ~]# iptables -F
[root@s2 ~]# iptables -t nat -F
[root@s2 ~]# iptables -t raw -F
[root@s2 ~]# iptables -t mangle -F
2、在網關防火牆上兩塊網卡
[root@s2 ~]# ifconfig
eth0 Link encap:Ethernet HWaddr 00:0C:29:87:17:A0
inet addr:192.168.10.10 Bcast:192.168.10.255 Mask:255.255.255.0
inet6 addr: fe80::20c:29ff:fe87:17a0/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:53 errors:0 dropped:0 overruns:0 frame:0
TX packets:80 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:5525 (5.3 KiB) TXbytes:13431 (13.1 KiB)
Interrupt:59 Base address:0x2000
eth1 Link encap:Ethernet HWaddr 00:0C:29:87:17:AA
inet addr:200.100.100.1 Bcast:200.100.100.255 Mask:255.255.255.0
確認網關上可以ping通內網客戶機，外網客戶機
[root@s2 ~]# ping 192.168.10.3
PING 192.168.10.3 (192.168.10.3) 56(84) bytes of data.
64 bytes from 192.168.10.3: icmp_seq=1ttl=128 time=1.22 ms
--- 192.168.10.3 ping statistics ---
1 packets transmitted, 1 received, 0%packet loss, time 0ms
rtt min/avg/max/mdev =1.225/1.225/1.225/0.000 ms
[root@s2 ~]# ping 200.100.100.2
PING 200.100.100.2 (200.100.100.2) 56(84) bytes of data.
64 bytes from 200.100.100.2: icmp_seq=1ttl=64 time=1.68 ms
64 bytes from 200.100.100.2: icmp_seq=2ttl=64 time=0.375 ms
64 bytes from 200.100.100.2: icmp_seq=3ttl=64 time=0.175 ms
--- 200.100.100.2 ping statistics ---
3 packets transmitted, 3 received, 0%packet loss, time 1999ms
rtt min/avg/max/mdev =0.175/0.744/1.682/0.668 ms
3、確認開啓路由轉發
[root@s2 ~]# vi /etc/sysctl.conf
net.ipv4.ip_forward = 1
[root@s2 ~]# sysctl -p
net.ipv4.ip_forward = 1
net.ipv4.conf.default.rp_filter = 1
net.ipv4.conf.default.accept_source_route =0
kernel.sysrq = 0
kernel.core_uses_pid = 1
net.ipv4.tcp_syncookies = 1
kernel.msgmnb = 65536
kernel.msgmax = 65536
kernel.shmmax = 4294967295
kernel.shmall = 268435456
4、在網關上添加DNAT映射，對於訪問網關80端口的數據包，將目標地址改爲網站服務器的ip地址的內網IP地址
[root@s2 ~]# iptables -t nat -A PREROUTING-i eth1 -d 200.100.100.1 -p tcp --dport 80 -j DNAT --to-destination192.168.10.3
5、外網用戶訪問內網的Web服務器測試下
SNAT策略應用
1、清空所有表的防火牆
[root@s2 ~]# iptables -F
[root@s2 ~]# iptables -t nat -F
[root@s2 ~]# iptables -t raw -F
[root@s2 ~]# iptables -t mangle -F
2、在網關防火牆上兩塊網卡
[root@s2 ~]# ifconfig
eth0 Link encap:Ethernet HWaddr 00:0C:29:87:17:A0
inet addr:192.168.10.10 Bcast:192.168.10.255 Mask:255.255.255.0
inet6 addr: fe80::20c:29ff:fe87:17a0/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:53 errors:0 dropped:0 overruns:0 frame:0
TX packets:80 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:5525 (5.3 KiB) TX bytes:13431(13.1 KiB)
Interrupt:59 Base address:0x2000
eth1 Link encap:Ethernet HWaddr 00:0C:29:87:17:AA
inet addr:200.100.100.1 Bcast:200.100.100.255 Mask:255.255.255.0
確認網關上可以ping通內網客戶機，外網客戶機
[root@s2 ~]# ping 192.168.10.3
PING 192.168.10.3 (192.168.10.3) 56(84) bytes of data.
64 bytes from 192.168.10.3: icmp_seq=1ttl=128 time=1.22 ms
--- 192.168.10.3 ping statistics ---
1 packets transmitted, 1 received, 0%packet loss, time 0ms
rtt min/avg/max/mdev =1.225/1.225/1.225/0.000 ms
[root@s2 ~]# ping 200.100.100.2
PING 200.100.100.2 (200.100.100.2) 56(84) bytes of data.
64 bytes from 200.100.100.2: icmp_seq=1ttl=64 time=1.68 ms
64 bytes from 200.100.100.2: icmp_seq=2ttl=64 time=0.375 ms
64 bytes from 200.100.100.2: icmp_seq=3ttl=64 time=0.175 ms
--- 200.100.100.2 ping statistics ---
3 packets transmitted, 3 received, 0%packet loss, time 1999ms
rtt min/avg/max/mdev =0.175/0.744/1.682/0.668 ms
3、確認開啓路由轉發
[root@s2 ~]# vi /etc/sysctl.conf
net.ipv4.ip_forward = 1
[root@s2 ~]# sysctl -p
net.ipv4.ip_forward = 1
net.ipv4.conf.default.rp_filter = 1
net.ipv4.conf.default.accept_source_route =0
kernel.sysrq = 0
kernel.core_uses_pid = 1
net.ipv4.tcp_syncookies = 1
kernel.msgmnb = 65536
kernel.msgmax = 65536
kernel.shmmax = 4294967295
kernel.shmall = 268435456
6、爲局域網訪問Internet的數據的包採用SNAT策略，將源地址更改爲服務器的公網的IP
地址
[root@s2 ~]# iptables -t nat -A POSTROUTING-s 192.168.10.0/24 -j SNAT --to-source 200.100.100.1
7、內網客戶機訪問外網Web服務器測試