NAT

目录

一.NAT概念

1.作用

2.NAT的使用场景

3.NAT的优点

二.拓扑图

1.静态NAT(一个内网地址对一个公网地址)

 2.动态NAT——PAT(多个内网地址对多个公网地址)

 3.Easyip(多个内网地址对一个接口)

 4.静态PAT(一对一,但是外网口IP和服务映射网内网服务器的IP和服务)


一.NAT概念

NAT—— Network Address Translation。又称为网络地址转换。

1.作用

用于实现私有网络和公有网络之间的互访

内网地址范围:

10.0.0.0——10.255.255.255

172.16.0.0——172.31.255.255

192.168.0.0——192.168.255.255

2.NAT的使用场景

  • 没有足够的公网IP连接到Internet
  • 当更换ISP(互联网服务提供商)需要重新编址
  • 合并两个使用重叠地址空间的内部网络
  • 使用单个IP地址支持基本的负载分担

3.NAT的优点

  • 节省了公网的IP地址
  • 能够处理编址方案重叠的情况
  • 网络发生改变时不需要重新编址
  • 隐藏了真正的IP地址(保证了安全)

二.拓扑图

1.静态NAT(一个内网地址对一个公网地址)

R1
<Huawei>u t m
Info: Current terminal monitor is off.
<Huawei>sys
Enter system view, return user view with Ctrl+Z.
[Huawei]sys r1
[r1]user-interface console 0
[r1-ui-console0]idle-timeout 0 0
[r1-ui-console0]q
[r1]int g0/0/0
[r1-GigabitEthernet0/0/0]ip add 192.168.1.1 24
[r1-GigabitEthernet0/0/0]undo shutdown 
Info: Interface GigabitEthernet0/0/0 is not shutdown.
[r1-GigabitEthernet0/0/0]q
[r1]int g0/0/1
[r1-GigabitEthernet0/0/1]ip add 202.10.100.1 24
[r1-GigabitEthernet0/0/1]undo shutdown
Info: Interface GigabitEthernet0/0/1 is not shutdown.
[r1-GigabitEthernet0/0/1]q
[r1]ip route-static 0.0.0.0 0 202.10.100.2
[r1]int g0/0/1
[r1-GigabitEthernet0/0/1]nat static global 15.0.0.10 inside 192.168.1.10 netmask
 255.255.255.255
[r1-GigabitEthernet0/0/1]display nat static 
  Static Nat Information:
  Interface  : GigabitEthernet0/0/1
    Global IP/Port     : 15.0.0.10/---- 
    Inside IP/Port     : 192.168.1.10/----
    Protocol : ----     
    VPN instance-name  : ----                            
    Acl number         : ----
    Netmask  : 255.255.255.255 
    Description : ----

  Total :    1
ISP
<Huawei>u t m
Info: Current terminal monitor is off.
<Huawei>sys
Enter system view, return user view with Ctrl+Z.
[Huawei]sys ISP	
[ISP]user-interface console 0
[ISP-ui-console0]idle-timeout 0 0
[ISP-ui-console0]q
[ISP]int g0/0/0
[ISP-GigabitEthernet0/0/0]ip add 202.10.100.2 24
Info: Interface GigabitEthernet0/0/0 is not shutdown.
[ISP-GigabitEthernet0/0/0]q
[ISP]ip route-static 15.0.0.10 32 202.10.100.1

测试结果PC1能ping通 PC2不行

 2.动态NAT——PAT(多个内网地址对多个公网地址)

R1
<Huawei>u t m
Info: Current terminal monitor is off.
<Huawei>sys
Enter system view, return user view with Ctrl+Z.
[Huawei]sys r1
[r1]user-interface console 0
[r1-ui-console0]idle-timeout 0 0
[r1-ui-console0]q
[r1]int g0/0/0
[r1-GigabitEthernet0/0/0]ip add 192.168.1.1 24
[r1-GigabitEthernet0/0/0]undo shutdown 
Info: Interface GigabitEthernet0/0/0 is not shutdown.
[r1-GigabitEthernet0/0/0]q
[r1]int g0/0/1
[r1-GigabitEthernet0/0/1]ip add 202.10.100.1 24
[r1-GigabitEthernet0/0/1]undo shutdown
Info: Interface GigabitEthernet0/0/1 is not shutdown.
[r1-GigabitEthernet0/0/1]q
[r1]ip route-static 0.0.0.0 0 202.10.100.2
[r1]nat address-group 1 15.0.0.10 15.0.0.11
[r1-GigabitEthernet0/0/1]acl 2000
[r1-acl-basic-2000]rule permit source 192.168.1.0 0.0.0.255
[r1-acl-basic-2000]q
[r1]int g0/0/1	
[r1-GigabitEthernet0/0/1]nat outbound 2000 address-group 1
[r1-GigabitEthernet0/0/1]display nat outbound 
 NAT Outbound Information:
 --------------------------------------------------------------------------
 Interface                     Acl     Address-group/IP/Interface      Type
 --------------------------------------------------------------------------
 GigabitEthernet0/0/1         2000                              1       pat
 --------------------------------------------------------------------------
  Total : 1
ISP
<Huawei>u t m
Info: Current terminal monitor is off.
<Huawei>sys
Enter system view, return user view with Ctrl+Z.
[Huawei]sys ISP	
[ISP]user-interface console 0
[ISP-ui-console0]idle-timeout 0 0
[ISP-ui-console0]q
[ISP]int g0/0/0
[ISP-GigabitEthernet0/0/0]ip add 202.10.100.2 24
Info: Interface GigabitEthernet0/0/0 is not shutdown.
[ISP-GigabitEthernet0/0/0]q
[ISP]ip route-static 15.0.0.0 24 202.10.100.1

 测试结果PC1能ping通 PC2也能ping通

 3.Easyip(多个内网地址对一个接口)

R1
<Huawei>u t m
Info: Current terminal monitor is off.
<Huawei>sys
Enter system view, return user view with Ctrl+Z.
[Huawei]sys r1
[r1]user-interface console 0
[r1-ui-console0]idle-timeout 0 0
[r1-ui-console0]q
[r1]int g0/0/0
[r1-GigabitEthernet0/0/0]ip add 192.168.1.1 24
[r1-GigabitEthernet0/0/0]undo shutdown 
Info: Interface GigabitEthernet0/0/0 is not shutdown.
[r1-GigabitEthernet0/0/0]int g0/0/1
[r1-GigabitEthernet0/0/1]ip add 202.10.100.1 24
[r1-GigabitEthernet0/0/1]undo shutdown
Info: Interface GigabitEthernet0/0/1 is not shutdown.
[r1-GigabitEthernet0/0/1]q
[r1]ip route-static 0.0.0.0 0 202.10.100.2
[r1]acl 2000
[r1-acl-basic-2000]rule permit source 192.168.1.0 0.0.0.255
[r1-acl-basic-2000]q
[r1]int g0/0/1
[r1-GigabitEthernet0/0/1]nat outbound 2000
[r1-GigabitEthernet0/0/1]display nat outbound 
 NAT Outbound Information:
 --------------------------------------------------------------------------
 Interface                     Acl     Address-group/IP/Interface      Type
 --------------------------------------------------------------------------
 GigabitEthernet0/0/1         2000                   202.10.100.1    easyip  
 --------------------------------------------------------------------------
  Total : 1
ISP
<Huawei>u t m
Info: Current terminal monitor is off.
<Huawei>sys
Enter system view, return user view with Ctrl+Z.
[Huawei]sys ISP	
[ISP]user-interface console 0
[ISP-ui-console0]idle-timeout 0 0
[ISP-ui-console0]q
[ISP]int g0/0/0
[ISP-GigabitEthernet0/0/0]ip add 202.10.100.2 24
Info: Interface GigabitEthernet0/0/0 is not shutdown.
[ISP-GigabitEthernet0/0/0]q
[ISP]ip route-static 15.0.0.0 24 202.10.100.1

  测试结果PC1能ping通 PC2也能ping通

 4.静态PAT(一对一,但是外网口IP和服务映射网内网服务器的IP和服务)

R1
<Huawei>u t m
Info: Current terminal monitor is off.
<Huawei>sys
Enter system view, return user view with Ctrl+Z.
[Huawei]sysname r1
[r1]user-interface console 0
[r1-ui-console0]idle-timeout 0 0
[r1-ui-console0]q
[r1]int g0/0/0
[r1-GigabitEthernet0/0/0]ip add 192.168.1.1 24
[r1-GigabitEthernet0/0/0]undo shutdown 
Info: Interface GigabitEthernet0/0/0 is not shutdown.
[r1-GigabitEthernet0/0/0]int g0/0/1
[r1-GigabitEthernet0/0/1]ip add 202.10.100.1 24
[r1-GigabitEthernet0/0/1]undo shutdown
Info: Interface GigabitEthernet0/0/1 is not shutdown.
[r1-GigabitEthernet0/0/1]q
[r1]ip route-static 0.0.0.0 0 202.10.100.2
[r1]int g0/0/1
[r1-GigabitEthernet0/0/1]nat server protocol tcp global 15.0.0.10 ftp inside 192
.168.1.10 ftp 
[r1-GigabitEthernet0/0/1]display nat server

  Nat Server Information:
  Interface  : GigabitEthernet0/0/1
    Global IP/Port     : 15.0.0.10/21(ftp) 
    Inside IP/Port     : 192.168.1.10/21(ftp)
    Protocol : 6(tcp)   
    VPN instance-name  : ----                            
    Acl number         : ----
    Description : ----

  Total :    1
[r1-GigabitEthernet0/0/1]q
[r1]nat alg all enable 
ISP
<Huawei>u t m
Info: Current terminal monitor is off.
<Huawei>sys
Enter system view, return user view with Ctrl+Z.
[Huawei]sys ISP	
[ISP]user-interface console 0
[ISP-ui-console0]idle-timeout 0 0
[ISP-ui-console0]q
[ISP]int g0/0/0
[ISP-GigabitEthernet0/0/0]ip add 202.10.100.2 24
Info: Interface GigabitEthernet0/0/0 is not shutdown.
[ISP-GigabitEthernet0/0/0]q
[ISP]ip route-static 15.0.0.10 32 202.10.100.1

 服务的开启 

### NAT 网络地址转换的工作原理 NAT(Network Address Translation),即网络地址转换,是一种用于修改网络数据包头中源地址或目的地址的技术[^1]。通过这种方式,NAT使得位于不同网络环境下的设备能够相互通信。 对于内部网络中的私有IP地址而言,在这些设备尝试连接至互联网或其他公共网络时,其原始的私有IP会被替换为合法的公网IP;反之亦然——来自外部的数据包到达边界路由器后,目标地址由公网IP变更为对应的内网私有IP。此过程不仅限于IPv4环境中,在某些情况下也适用于IPv6场景下实现跨版本互访的需求。 #### 动态NAT特性说明 动态NAT允许内部网络内的多个节点共享有限数量的真实全球唯一可路由的IP资源来访问外界服务。具体来说: - **多对一或多对多映射**:不同于静态一对一的形式,这里可以是一组内部地址对应单个或几个外部出口地址; - **按需分配原则**:每当一台机器发起对外请求时才临时获取一个可用的公有IP作为代理身份参与通信活动,结束后立即释放以便其他成员继续借用; - **受限于地址池大小**:如果当前在线并发量超过了预设好的可供变换使用的公网号段总数,则超出部分可能无法正常上网[^3]。 ### 配置方法实例展示 以下是基于华为系列路由器平台的一个简单配置案例,旨在演示如何设置基本形式的静态与动态两种模式下的NAT功能。 #### 静态NAT配置命令序列 ```shell [R1]interface GigabitEthernet0/0/1 //进入外网接口视图 [R1-GigabitEthernet0/0/1]nat static global 8.8.8.8 inside 192.168.10.10 //定义一条固定的内外部地址映射关系 [R1]display nat static //查看已生效的所有静态条目详情 ``` 这段脚本实现了将特定的一台内部服务器(拥有固定不变的LAN侧标识`192.168.10.10`)暴露给广域网上指定位置(`8.8.8.8`)的功能,从而让远端客户可以直接通过后者寻址并建立TCP/IP会话链接[^4]。 #### 动态NAT配置概览 为了使更多不确定数量和确切ID的企业终端都能顺利触达因特网空间而不必各自申请独立的身份标签,管理员可以选择开启动态机制: ```shell //假设已经预先规划好了一个范围足够覆盖所有潜在需求者的弹性IP集合,并命名为pool_1 ip nat pool pool_1 start-ip end-ip netmask subnet-mask access-list acl_id permit ip any host internal_network_segment ip nat inside source list acl_id pool pool_1 overload ``` 上述指令集创建了一套灵活应对大规模局域网接入情况的基础框架,其中涉及到了地址池(pool)以及访问控制列表(acl)两个核心组件的设计思路。
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