[转]Network Address Translation [size=18][color=darkred]Network Address Translation[/color][/size] yUmi#sh start ! Written by yUmis(牛奶咖喱) a.k.a. 红头发 Description 欢迎转po,请保留作者信息 Homepage http://www.show-tym.com Jun.28th.2004 ! NAT术语: [img]http://www.show-tym.com/bbs/data/ca/aa.JPG[/img] inside:需要翻译成外部地址的网络 outside:外部地址,Internet地址 local:出现于内网 global:出现于外网 [img]http://www.show-tym.com/bbs/data/ca/bb.JPG[/img] inside local:分配给处于内网的主机的IP地址,地址是全局唯一的,一般分配的是由RFC 1918里定义的私有地址(private IP address) inside global:用来替代inside local的对外的,可用于Internet上的地址,即被翻译后的地址.地址全局唯一,由ISP分配 [img]http://www.show-tym.com/bbs/data/ca/cc.JPG[/img] outside local:外网主机相对于内网所用的IP地址.地址可以从RFC 1918中定义的进行分配 outside global:分配给外网主机的外部地址 simple translation entry:把一个IP地址映射到另外一个地址上去的翻译方式 extended translation entry:把IP地址和端口(port)的组合翻译成另外一个地址和端口的组合 static address translation:静态翻译,把一个local对应到global上去 dynamic address translation:动态翻译,local和global池(pool)建立动态对应关系 port address translation(PAT):通过使用地址和端口的结合来达到多个local对应一个global的状态.端口号用来区别不同的local.这样的技术也叫overloading.如下图: [img]http://www.show-tym.com/bbs/data/ca/dd.JPG[/img] 如何配置NAT? 接口配置模式下: 1.配置NAT为inside/ouside: ip nat { inside | outside } 在全局配置模式下: 2.定义地址池的起始地址和完结地址,掩码等: ip nat pool <name>; <start-ip>; <end-ip>; { netmask <netmask>; | prefix-length <prefix-length>; } [ type { rotary } ] 3.启用inside源地址翻译: ip nat inside source { list <acl>; pool <name>; [overload] | static <local-ip>;<global-ip>; } list <acl>; pool <name>; [overload]是动态翻译,匹配ACL的包翻译成地址池里的global地址.可选参数overload允许TCP/UDP的端口翻译(多对一的映射) static <local-ip>;<global-ip>;为静态翻译 4.启用inside目标地址翻译: ip nat inside destination { list <acl>; pool <name>; | static <global-ip>; <local-ip>; } 5.启用outside源地址翻译: ip nat outside source { list <acl>; pool <name>; | static <global-ip>; <local-ip>; } list <acl>; pool <name>;为动态翻译 static <global-ip>; <local-ip>;为静态翻译 6.启用outside目标地址翻译: ip nat outside source { list <acl>; pool <name>; | static <global-ip>; <local-ip>; } 7.配置NAT超时设置: ip nat translation timeout <seconds>; 特权模式下(EXEC mode): 8.查看生效的NAT设置: show ip nat translations [ verbose ] 9.查看NAT统计信息: show ip nat statistics 10.清除所有动态NAT配置: clear ip nat translation * 11.清除单个动态NAT配置: clear ip nat translation <global-ip>; 12.清除特定NAT配置: clear ip nat translation <global-ip>; <local-ip>; <protocol>; <global-port>; <local-port>; 13.debug: debug ip nat [ <list>; ] [ detailed ] 一些高级配置: 1.更灵活的地址池的配置: ip nat pool <name>; { netmask <mask>; | prefix-length <length>; } [ type { rotary } ] 这样可以允许定义不连续地址池,接下来定义地址空间: address <start>; <end>; 例子: Router(config)#ip nat pool fred prefix-length 24 Router(config-ipnat-pool)#address 171.69.233.225 171.69.233.226 Router(config-ipnat-pool)#address 171.69.233.228 171.69.233.238 这样就定义了一个171.69.233.225-226和and 171.69.233.228-238的地址池 2.翻译为接口地址: ip nat inside source list <number>; interface <interface>; overload 如果接口shut或者接口没有设置IP地址的话,NAT不会生效 3.映射某个服务到某个主机上(比如邮件服务): ip nat inside source static { tcp | udp } <localaddr>; <localport>; <globaladdr>; <globalport>; 4.对route map的支持: ip nat inside source route-map <name>; pool <name>; 例子: ip nat pool provider1-space 171.69.232.1 171.69.232.254 prefix-length 24 ip nat pool provider2-space 131.108.43.1 131.108.43.254 prefix-length 24 ip nat inside source route-map provider1-map pool provider1-space ip nat inside source route-map provider2-map pool provider2-space ! interface Serial0/0 ip nat outside ! interface Serial0/1 ip nat outside ! interface Fddi1/0 ip nat inside ! route-map provider1-map permit 10 match ip address 1 match interface Serial0/0 ! route-map provider2-map permit 10 match ip address 1 match interface Serial0/1 Fin PDF下载: http://www.show-tym.com/bbs/zboard.php?id=works&page=1&sn1=&divpage=1&sn=off&ss=on&sc=on&select_arrange=headnum&desc=asc&no=19 . [ 关闭窗口 ]