弱电学习CCNA课件-第18章 NAT.pdf

第十八章网络地址翻译 NAT主讲人：ALLENNAT网络地址翻译 随着Internet的飞速发展，网上丰富的资源产生着巨大的吸引力接入Internet成为当今信息业最为迫切的需求但这受到IP地址的许多限制首先，许多局域网在未联入Internet之前，就已经运行许多年了，局 域网上有了许多现成的资源和应用程序，但它的IP地址分配不符合 Internet的国际标准，因而需要重新分配局域网的IP地址，这无疑是 劳神费时的工作其二，随着Internet的膨胀式发展，其可用的IP地址越来越少，要想 在ISP处申请一个新的IP地址已不是很容易的事了NAT（网络地址翻译）能解决不少令人头疼的问题它解决问题的办法是：在内部网络中使用内部地址，通过NAT把内部地址翻译成合法的IP地址，在Internet上使用其具体的做法是把IP包内的地址池（内部本地）用合法的IP地址段（内部全局）来替换Chapter ActivitiesWindows 95 PCModemBranch officeISDN/analogSmall officeCentral siteFrame RelayFrame RelayservicePRIBRIBRIFrame RelayAsyncAAA serverAsyncSA10.1.1.1166.1.1.1SAInside Local IP Address10.1.1.1Inside Global IP Address166.1.1.1NAT table PATNAT 术语NAT 功能NAT 三种类型NAT 术语InternetInside10.1.1.1Inside Local IP Address10.1.1.1Simple NAT tableInside Global IP Address166.1.1.110.1.1.2Host B172.20.7.3ACBABDSA10.1.1.1DA10.1.1.1SA166.1.1.1DA166.1.1.1DC内部本地地址:私有IP，不能直接用于互连网。内部全局地址：用来代替内部本地IP地址的，对外，或在互联网上是合法的的IP地址。NAT 功能Inside Local IP Address10.1.1.110.1.1.2NAT tableInside Global IP Address196.168.2.2196.168.2.3NAT 功能:内部网络地址转换复用内部的全局地址TCP 负载均衡解决网络地址重叠InternetInside10.1.1.110.1.1.2复用内部的全局地址将一个内部全局地址用于同时代表多个内部局部地址。主要用IP地址和端口号的组合来唯一区分各个内部主机。目前在公司内普遍应用。（如下图）复用内部的全局地址10.1.1.2:172310.1.1.1:1024NAT table196.168.2.2:1723196.168.2.2:1024TCPTCP10.1.1.3:1492196.168.2.2:1492TCPInternetInside10.1.1.1Host B179.20.7.313SA10.1.1.1DA10.1.1.1SA196.168.2.2DA196.168.2.210.1.1.210.1.1.3452Host C179.21.7.3DA196.168.2.24Inside Global IP Address: PortProtocolInside Local IP Address: Port10.1.1.1TCP 负载均衡TCP 负载均衡：用于将一台虚拟的主机映射到几台真实的主机上。(如下图)TCP 负载均衡NAT tableInside Global IP Address: Port 10.1.1.127:8010.1.1.127:8010.1.1.127:80ProtocolTCPTCPTCPInside Local IP Address: Port10.1.1.1:8010.1.1.2:8010.1.1.3:80InternetInside10.1.1.1Host B176.20.7.345SA10.1.1.1DA10.1.1.1SA10.1.1.127DA10.1.1.12710.1.1.210.1.1.1132Host C176.21.7.310.1.1.12710.1.1.3VirtualhostRealhostsNAT三种类型NAT有三种类型：静态NAT（staticNAT）、NAT池（pooledNAT）和端口NAT（PAT）。其中静态NAT设置起来最为简单，内部网络中的每个主机都被永久映 射成 外部网络中的某个合法的地址,多用于服务器。而NAT池则是在外部网络中定义了一系列的合法地址，采用动态分配 的方法映射到内部网络,多用于网络中的工作站。PAT则是把内部地址映射到外部网络的一个IP地址的不同端口上。NAT静态映射实例interface Ethernet0ip address 172.16.1.1 255.255.255.0ip nat inside（指定内部接口）!interface Serial0 ip address 200.1.1.1 255.255.255.0 ip nat outside （指定外部接口）!ip nat inside source static 172.16.1.3 200.1.1.1(建立两个IP地址之间的静态映射)ip classlessip route 0.0.0.0 0.0.0.0 200.1.1.2注意：从外网到内网建立静态映射后，外网能PING通内部全局地址（200.1.1.1）,如果使用真实地址，则访问失败，这是因为从外网没有到达内网的路由存在！Ping 172.16.1.3 Ping 200.1.1.5 !ip nat pool dyn-nat 192.16.2.1 192.16.2.254 netmask 255.255.255.0ip nat inside source list 1 pool dyn-nat!interface Ethernet0 ip address 10.1.1.1 255.255.255.0 ip nat inside!interface Serial0 ip address 192.16.2.1 255.255.255.0 ip nat outside! access-list 1 permit 10.1.1.0 0.0.0.255!动态NAT的配置Translate between inside hosts addressed from 10.1.1.0/24 to the globally unique 192.16.2.0/24 network. This interface connected to the outside world. This interface connected to the inside network. PAT的配置ip nat pool ovrld-nat 192.16.2.1 192.16.2.2netmask 255.255.255.0ip nat inside source list 1 pool ovrld-nat overload!interface Ethernet0/0 ip address 10.1.1.1 255.255.255.0 ip nat inside!interface Serial0/0 ip address 192.16.2.1 255.255.255.0 ip nat outside!access-list 1 permit 10.1.1.0 0.0.0.255Router#sh ip nat trans clear ip nat trPro Inside global Inside local Outside local Outside globaltcp 192.2.2.1:11003 10.1.1.1:11003 172.16.2.2:23 172.16.2.2:23tcp 192.2.2.1:1067 10.1.1.2:1067 172.16.2.3:23 172.16.2.3:23Verifying NATA translation for a Telnet is still active. Two different inside hosts appear on the outside with a single IP address.Basic IP address translation Unique TCP port numbers are used to distinguishbetween hosts. Router#show ip nat transPro Inside globalInside localOutside local Outside global-192.2.2.110.1.1.1- - -192.2.2.210.1.1.2- -IP address translation with overloadingRouter#debug ip natNAT: s=10.1.1.1-192.16.2.1, d=172.166.2.2 0NAT*: s=172.166.2.2, d=192.16.2.1-10.1.1.1 0NAT: s=10.1.1.1-192.16.2.1, d=172.166.2.2 1NAT: s=10.1.1.1-192.16.2.1, d=172.166.2.2 2NAT: s=10.1.1.1-192.16.2.1, d=172.166.2.2 3NAT*: s=172.166.2.2, d=192.16.2.1-10.1.1.1 1NAT: s=10.1.1.1-192.16.2.1, d=172.166.2.2 4NAT: s=10.1.1.1-192.16.2.1, d=172.166.2.2 5NAT: s=10.1.1.1-192.16.2.1, d=172.166.2.2 6NAT*: s=172.166.2.2, d=192.16.2.1-10.1.1.1 2Troubleshooting NATAn example address translation inside-to-outside.A reply to the packet sent.An example TCP conversation, inside-to-outside.* Indicates translation was in the fast path.Clearing NAT Translation EntriesAll entries are cleared.192.16.2.2 is cleared.Router#sh ip nat transPro Inside global Inside local Outside local Outside globaltcp 192.16.2.1:11003 10.1.1.1:11003 172.16.2.2:23 172.16.2.2:23tcp 192.16.2.1:1067 10.1.1.2:1067 172.16.2.3:23 172.16.2.3:23router#clear ip nat trans *router#router#show ip nat trans router#show ip nat transPro Inside global Inside local Outside localOutside globaludp 192.16.2.2:1220 10.1.1.2:1120 171.69.2.132:53 171.69.2.132:53 tcp 192.16.2.1:11003 10.1.1.1:11003 172.16.2.2:23 172.16.2.2:23tcp 192.16.2.1:1067 10.1.1.1:1067 172.16.2.3:23 172.16.2.3:23router#clear ip nat trans udp inside 192.16.2.2 10.1.1.2 1220171.69.2.132 53 171.69.2.132 53 router#show ip nat transPro Inside global Inside local Outside localOutside globaltcp 192.16.2.1:11003 10.1.1.1:11003 172.16.2.2:23 172.16.2.2:23tcp 192.16.2.1:1067 10.1.1.3:1067 172.16.2.3:23 172.16.2.3:23