Linux：iptables防火墙部署优化之路由转发（地址伪装）

Linux：iptables防火墙部署优化之路由转发（地址伪装）

准备工作：

​ 1.已知node2的主机名称为node2.timinglee.org其ip为192.168.0.200

​ 2.已知node1的主机名为node1.timinglee.org,此主机为双网卡主机其IP为172.25.254.200和192.168.0.100，请在此主机中配置策略可以使node2主机访问外网

node1主机操作

检测ip情况

#查看网卡的ip信息
[root@node1 ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 00:0c:29:33:49:40 brd ff:ff:ff:ff:ff:ff
    altname enp3s0
    altname ens160
    inet 172.25.254.200/24 brd 172.25.254.255 scope global noprefixroute eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::fa94:b632:5bd6:a146/64 scope link noprefixroute
       valid_lft forever preferred_lft forever
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 00:0c:29:33:49:4a brd ff:ff:ff:ff:ff:ff
    altname enp19s0
    altname ens224
    inet 192.168.0.100/24 brd 192.168.0.255 scope global noprefixroute eth1
       valid_lft forever preferred_lft forever
    inet6 fe80::518f:2870:1a4c:178f/64 scope link noprefixroute
       valid_lft forever preferred_lft forever
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关闭firewalld防火墙服务，并锁定该服务

[root@node1 ~]# systemctl disable --now firewalld.service
Removed "/etc/systemd/system/multi-user.target.wants/firewalld.service".
Removed "/etc/systemd/system/dbus-org.fedoraproject.FirewallD1.service".

# 锁定firewalld服务
[root@node1 ~]# systemctl mask firewalld.service
Created symlink /etc/systemd/system/firewalld.service → /dev/null.
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开启iptables服务

[root@node1 ~]# systemctl enable --now iptables.service
Created symlink /etc/systemd/system/multi-user.target.wants/iptables.service → /usr/lib/systemd/system/iptables.service.
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清空iptables的默认策略

[root@node1 ~]# iptables -F
[root@node1 ~]# iptables -nL
Chain INPUT (policy ACCEPT)
target     prot opt source               destination

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination
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开启内核路由转发功能

# 发现内核路由转发功能未开启
[root@node1 ~]# sysctl -a | grep ip_forward
net.ipv4.ip_forward = 0
net.ipv4.ip_forward_update_priority = 1
net.ipv4.ip_forward_use_pmtu = 0

# 修改配置文件，开启内核路由转发功能
[root@node1 ~]# vim /etc/sysctl.conf
[root@node1 ~]# sysctl -p
net.ipv4.ip_forward = 1

[root@node1 ~]# sysctl -a | grep ip_forward
net.ipv4.ip_forward = 1
net.ipv4.ip_forward_update_priority = 1
net.ipv4.ip_forward_use_pmtu = 0
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配置iptables的策略，实现地址伪装（路由转化），从而使得node2主机可以访问外网

[root@node1 ~]# iptables -t nat -A POSTROUTING -o eth0 -j SNAT --to-source 172.25.254.200

[root@node1 ~]# iptables -t nat -nL
Chain PREROUTING (policy ACCEPT)
target     prot opt source               destination

Chain INPUT (policy ACCEPT)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

Chain POSTROUTING (policy ACCEPT)
target     prot opt source               destination
SNAT       all  --  0.0.0.0/0            0.0.0.0/0            to:172.25.254.200
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永久保存策略

[root@node1 ~]# service iptables save
iptables: Saving firewall rules to /etc/sysconfig/iptables: [  OK  ]
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node2主机操作

检测ip情况

#查看网卡的ip信息
[root@node2 ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 00:0c:29:8c:36:ce brd ff:ff:ff:ff:ff:ff
    altname enp3s0
    altname ens160
    inet 192.168.0.200/24 brd 192.168.0.255 scope global noprefixroute eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::fecd:4c84:736e:eae/64 scope link noprefixroute
       valid_lft forever preferred_lft forever
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修改node2的网关以及dns

[root@node2 ~]# vim /etc/NetworkManager/system-connections/eth0.nmconnection
[ipv4]
address1=192.168.0.200/24,192.168.0.100
dns=114.114.114.114;
method=manual
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重启网卡配置文件

[root@node2 ~]# nmcli connection reload
[root@node2 ~]# nmcli connection up eth0
Connection successfully activated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/3)
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查看是否修改成功

[root@node2 ~]# cat /etc/resolv.conf
# Generated by NetworkManager
search timinglee.org
nameserver 114.114.114.114
[root@node2 ~]# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.0.100   0.0.0.0         UG    100    0        0 eth0
192.168.0.0     0.0.0.0         255.255.255.0   U     100    0        0 eth0
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测试看是否可以访问外网，测试成功

[root@node2 ~]# ping www.baidu.com
PING www.a.shifen.com (110.242.68.3) 56(84) bytes of data.
64 bytes from 110.242.68.3 (110.242.68.3): icmp_seq=1 ttl=127 time=54.3 ms
64 bytes from 110.242.68.3 (110.242.68.3): icmp_seq=2 ttl=127 time=65.6 ms
64 bytes from 110.242.68.3 (110.242.68.3): icmp_seq=3 ttl=127 time=49.2 ms
^C64 bytes from 110.242.68.3: icmp_seq=4 ttl=127 time=99.9 ms

--- www.a.shifen.com ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 30198ms
rtt min/avg/max/mdev = 49.160/67.248/99.925/19.780 ms
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