NAT的英文全称是Networking Address Translation

NAT(Network Address Translation)顾名思义就是网络IP地址的转换。NAT的出现是为了解决IP日益短缺的问题，将多个内部地址映射为少数几个甚至一个公网地址。同时它还起到了隐藏内部网络结构的作用，具有一定的安全性。NAT主要包括3种方式：PAT、动态NAT和静态NAT，PAT(Port Address Translation)也简称为NAPT，就是将多个内部地址映射为一个公网地址。这种方式常用于拨号上Internet网。其部分清单配置如下。

dial script. add set modem ABORT ERROR""ATZ OK ATL lMI&CI&D2&SOS0=0OK (1)

e0//设置e0的IP地址

ip add10.191.140.254 255.255.255.0

quit

s0//设置s0为PPP拨号方式

encapsulate PPP

line dial

idletime 180

init script. set modem//设置拨号脚本

login_script. login

def_phone XXX//设置ISP的拨入电话号码

nat enable//允许NAT出口

speed 115k

quit

route add default S0 1 (2)

nat inside source interface S0 (3)

动态NAT可以将多个内部地址映射为多个公网地址，常用于DDN专线上网。用户要得到多个公网地址，可以通过建立一个地址池，使大家共同使用这些公网地址。其部分清单配置如下。

ippool add ciu 202.103.23.1 14 (4)

e0//设置e0的IP地址

ipadd10.191.140.254255.255.255.0

quit

s0//设置s0为同步PPP专线方式，也可能为同步HDLC专线方式

encapsulate ppp (5)

port sync

ip add202.103.10.122255.255.255.252//设置端口地址

map add202.103.10.121 (6)

nat enable//允许NAT出口

quit

route add default 202.103.10.121 1//设置缺省路由

nat inside source pool ciu overload//设置为内部地址翻译，其中over load表示多个内部地址可同时使用一个公网地址。

静态NAT可以将内部地址与公网地址建立一一对应的关系，常用于对公网提供公众服务，如Web服务器。配置略。

请解释上述划线部分语句的含义?

Most IP layer-based proxy mechanisms, such as network address translation(NAT), only support uni-directional proxy, from the internal network to external network(the Internet). The proxy establishes the communication channel by(66)IP addresses. The IP addresses must be(67). These proxy mechanisms prevent applications that must establish return data channels from establishing their data channels, such as, multimedia applications. IP layer-based proxy mechanisms need additional software(68)for each application that uses(69)channels. SOCKS identifies communication targets through domain names, overcoming the restriction of using private IP addresses. SOCKS can use domain names to establish communication between separate LANs, with(70)IP addresses.

A．manufacturing

B．manipulating

C．conduct

D．implement

Most IP layer-based proxy mechanisms, such as network address translation(NAT), only support uni-directional proxy, from the internal network to external network(the Internet). The proxy establishes the communication channel by(86) IP addresses. The IP addresses must be(87). These proxy mechanisms prevent applications that must establish return data channels from establishing their data channels, such as, multimedia applications. IP layer-based proxy mechanisms need additional software(88)for each application that uses(89)channels. SOCKS identifies communication targets through domain names, overcoming the restriction of using private IP addresses. SOCKS can use domain names to establish communication between separate LANs, with(90)IP addresses.

A．manufacturing

B．manipulating

C．conduct

D．implement

防火墙一般都具有网络地址转换功能( Network Address Translation,NAT),NAT允许多台计算机使用一个( )连接网络:

A、 Web 浏览器

B、 IP 地址

C、 代理服务器

D、 服务器名

Most IP layer-based proxy mechanisms，such as network address translation (NAT)，only supportuni-directional proxy，from the internal network to external network(the Interned．The proxvestablishes the communication channel by (71) IP addresses．The IP addresses must be (72) ．These proxy mechanisms prevent applications that must establish return data channels from establishing their data channels，such as，multimedia applications．IP layer-based proxy mechanisms need additional software (73) for each application that uses (74) channels． SOCKS identifies communication targets through domain names，overcoming the restriction of Usina private IP addresses．SOCKS can use domain names to establish communication between separate LANs，with (75) IP addresses．

(66)

A．manufacturing

B．manipulating

C．conduct

D．implement

A. The summarized address for all internal subnetted addresses.

B. A private IP address assigned to a host on the inside network.

C. A registered address that represents an inside host to an outside network.

D. A unique IP address used on an internal network

E. Non of the above

ArouterthatperformsNetworkAddressTranslation（NAT）isinstalledbetweenyourcomputerandtheInternet.Therouterfails.YouconnectthecomputerdirectlytotheInternet.YouneedtoensurethatthecomputerisconnectedtotheInternetinthemostsecuremannerpossible.Whatshouldyoudo？（）

A.EnabletheRemoteDesktopfeatureintheSystemPropertiesdialogbox.

B.ConfigurethenetworkcategoryofyournetworkconnectiontoPublic.

C.ConfigurethenetworkcategoryofyournetworkconnectiontoPrivate.

D.EnabletheWindowsCollaborationComputerNameRegistrationServiceexceptioninMicrosoftWindowsFirewall.

A、网络地址端口转换

B、网络地址转换

C、网络端口地址转换

D、网络端口转换