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将 nat 解决方案插入到不是网关的网络中

tag-icon • tag-icon networking freebsd ip pf
将 nat 解决方案插入到不是网关的网络中

我尝试过几种不同的方法。目前正在 freebsd 8.2 上尝试使用 pf

我正在尝试将 nat 解决方案插入到现有网络中，该解决方案会将流量从外部 IP 地址重定向到所有端口上的内部 IP 地址（静态 nat），但我也想转换源地址。

当前网络。

hosta
192.168.1.2/24 

gw
192.168.1.1/24

outsidehost
10.0.0.1/24 

natbox
em0 192.168.1.3/24 (used to manage the box)
em1 10.0.0.2/24 (outside address same lan as outsidehost)
em0_alias0 192.168.1.4/24 (inside address same lan as hosta)
route 192.168.1.0/24 192.168.1.1
route 0.0.0.0 0.0.0.0 10.0.0.1

我希望 externalhost 能够通过 telneting(sp) 到 10.0.0.2 来 telnet 到 192.168.1.3

为此，我假设我必须在数据包离开 em0 时更改数据包的来源，否则它将在返回 em1 的途中丢失。

所以流程是这样的：

  • 从外部主机 telnet 10.0.0.2
  • 将源地址更改为192.168.1.4
  • 将 10.0.0.2 的流量重定向到 192.168.1.2
  • 数据包以 src 192.168.1.4 离开，转到 192.168.1.2，然后发送回 192.168.1.4，在本例中转换回源 addy 的值 10.0.0.1

我一直认为这可以做到

binat 和 rdr 但我无法弄清楚语法。

我怎样才能完成这件事？

答案1

我最终在 Linux 下使用 iptables 来完成这个任务。

为此，需要开启IP转发：

echo net.ipv4.ip_forward=1 >> /etc/sysctl.conf

并设定以下规则：

iptables -F -t nat
# flush the NAT Table.
iptables -t nat -P INPUT DROP
# set the input chain on the NAT table to DROP by default. 
# This way any traffic not allowed by defining a source address gets dropped.
# If you don't provide a -s address below it will allow all hosts from anywhere
# to reach the inside address via the outside ip. 

iptables -t nat -A PREROUTING -s 10.0.0.1 -d 10.0.0.2 \
         -j DNAT --destination-address 192.168.1.3 
# define the source and destination of the traffic allowed through.
# Change the dest address to our inside host. 

iptable -t nat -A INPUT -s 192.168.0.0/24 -J ALLOW
# Drop all traffic on sourcing from inside subnet. 
# This won't apply to traffic that matches the rule above
# as the source address will change in the next rule. 

iptables -t nat -A POSTROUTING -d 192.168.1.3 \
         -j SNAT --source-address 192.168.1.4
# here is the insert magic. Change the source address of any traffic destined
# for our inside host to our vip or owned inside address.
# This way the traffic is routed back to us at the FW.

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