推荐回答(2个)
如何配置NAT (网络地址转换),从而使得互联网上的计算机通过其思科路由器访问其内部的Web和电子邮件服务器。这需要在专门公用的IP地址和专门私用的IP地址之间配置一个静态的NAT转换。
通过处于外部的网络(也就是Internet)与内部的网络(也就是私有网络)之间的路由器配置一个静态的IP转换。
要获取网络内部和到达你的Web/邮件服务器的数据通信,可以采用两个重要的措施:
1.NAT配置
2.防火墙配置
不管正运用基本的访问控制列表(ACL)或者是正使用思科的IOS防火墙属性集(详细信息见:Cisco IOS firewall feature set),一定要确信你理解了思科IOS的操作顺序,这样才能为适当的IP地址(不管是公有的还是私有的)配置你的防火墙。换句话说,哪一个先发生呢?是 NAT转换,还是防火墙过滤?例如,在使用ACL时,一个输入的ACL检查要先于NAT转换。因此,你需要在头脑中牢牢记住拥有公有IP地址的ACL.
静态NAT配置interface Serial0/0
ip address 63.63.63.1 255.255.255.0
ip nat outside
interface Ethernet0/0
ip address 10.1.1.1 255.255.255.0
ip nat inside
使用了上述的端口数字,因为它们适合想要执行操作的描述。但是需要记住,端口数字可能会有所不同。关闭了用于SMTP(发送邮件)的 25号端口、用于HTTPS(安全Web)的443号端口,用于HTTP(Web通信)的80号端口,还关闭了用于POP3(从邮件服务器接收邮件)的 110号端口。
这个配置需要假定有一组IP地址。如果没有,可以使用路由器(此例中就是Serial 0/0)上的外部IP地址,可以进行如下配置:
router(config)#ip nat inside source static tcp 10.1.1.2 25 interface serial 0/0 25
如果有一个从ISP那里得到的动态的DHCP IP地址,甚至也可以使用这个命令。
还需要在公网Internet DNS服务器中注册这个邮件和Web服务器的IP地址。因此,当用户在其Web浏览器中键入www.mywebserver.com时,浏览器就会将其转化为63.63.63.2,路由器将会把它转换为10.1.1.2.Web服务器会接收这个请求,并通过路由器给予回应,路由器会再将其转换回公网IP地址。
除了配置静态的NAT,可能想到在这同时使用动态的NAT.有鉴于此,内部的PC可以使用动态的NAT为访问互联网(即NAT过载或PAT)。不过,这样就有点儿更加复杂。如果大家感兴趣,可以参考思科的Configuring Static and Dynamic NAT Simultaneously文档。
1. 写NAT转换列表如:
ip nat inside source static 172.16.1.10 210.28.1.10
//将内网的172.16.1.10 IP地址静态映射为外网的 210.28.1.10 公有IP地址
2. 在路由器接口上写调用:
ip nat inside(内网接口)或ip nat outside(外网出接口)
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