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使用 iptables 将 Ubuntu 用作 NAT 网关

tag-icon • tag-icon ubuntu iptables nat gateway
使用 iptables 将 Ubuntu 用作 NAT 网关

我正在尝试配置 U​​buntu 14.04 以充当私有网络和公共网络之间的 NAT 网关。

  • 公共接口 ->eth0 (178.x.x.x)
  • 私有接口 ->eth0:0 (192.168.206.190/17)

我尝试了许多iptables规则组合，但还是无法路由流量。我已确认网关可以看到互联网，私有网络上的主机可以看到网关，并且默认网关设置正确。

net.ipv4.ip_forward=1安顿好了sysctl。

我的iptables规则如下。我的iptables经验很少，所以很可能我遗漏了一些东西。

# Generated by iptables-save v1.4.21 on Thu Apr 21 12:38:44 2016
*security
:INPUT ACCEPT [215:14912]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [133:16208]
COMMIT
# Completed on Thu Apr 21 12:38:44 2016
# Generated by iptables-save v1.4.21 on Thu Apr 21 12:38:44 2016
*raw
:PREROUTING ACCEPT [215:14912]
:OUTPUT ACCEPT [133:16208]
COMMIT
# Completed on Thu Apr 21 12:38:44 2016
# Generated by iptables-save v1.4.21 on Thu Apr 21 12:38:44 2016
*nat
:PREROUTING ACCEPT [3:132]
:INPUT ACCEPT [3:132]
:OUTPUT ACCEPT [0:0]
:POSTROUTING ACCEPT [0:0]
-A POSTROUTING -o eth0 -j MASQUERADE
COMMIT
# Completed on Thu Apr 21 12:38:44 2016
# Generated by iptables-save v1.4.21 on Thu Apr 21 12:38:44 2016
*mangle
:PREROUTING ACCEPT [215:14912]
:INPUT ACCEPT [215:14912]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [133:16208]
:POSTROUTING ACCEPT [133:16208]
COMMIT
# Completed on Thu Apr 21 12:38:44 2016
# Generated by iptables-save v1.4.21 on Thu Apr 21 12:38:44 2016
*filter
:INPUT ACCEPT [46:3296]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [28:3484]
-A FORWARD -i eth0:0 -o eth0 -m state --state RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -i eth0 -o eth0:0 -j ACCEPT
COMMIT
# Completed on Thu Apr 21 12:38:44 2016

iptables -L -v

Chain INPUT (policy ACCEPT 15 packets, 1044 bytes)
 pkts bytes target     prot opt in     out     source               destination

Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination
    0     0 ACCEPT     all  --  eth0:0 eth0    anywhere             anywhere             state RELATED,ESTABLISHED
    0     0 ACCEPT     all  --  eth0   eth0:0  anywhere             anywhere

Chain OUTPUT (policy ACCEPT 10 packets, 1016 bytes)
 pkts bytes target     prot opt in     out     source               destination

以下是私有网络上主机的配置：

netstat -r
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
default         nat             0.0.0.0         UG        0 0          0 eth0
192.168.128.0   *               255.255.128.0   U         0 0          0 eth0

对“nat”执行 ping 操作确认主机可以看到“nat”：

ping nat
PING nat (192.168.206.190) 56(84) bytes of data.
64 bytes from nat (192.168.206.190): icmp_seq=1 ttl=64 time=0.359 ms

对 8.8.8.8 进行 ping 操作显示没有流量路由：

ping 8.8.8.8
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
^C
--- 8.8.8.8 ping statistics ---
3 packets transmitted, 0 received, 100% packet loss, time 1999ms

答案1

我认为问题出在这条规则上

-A FORWARD -i eth0:0 -o eth0 -m state --state RELATED,ESTABLISHED -j ACCEPT

你必须改变接口的位置

-A FORWARD -i eth0 -o eth0:0 -m state --state RELATED,ESTABLISHED -j ACCEPT

答案2

提供商 (Linode) 在虚拟机管理程序/网络级别按 IP 地址过滤流量，因此具有公共 IP 地址的流量根本不会穿越专用网络。我现在已经更换了提供商，NAT 运行正常。

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