為方便廣大考生考后估分對答案，希賽網特向廣大學員和網友搜集整理了相關真題信息，供大家參考。收集完整2021年上半年軟考網絡工程師真題答案后，希賽網的老師也將在考后第一時間進行真題答案解析，敬請廣大考友考后積極關注。

現在要推薦給大家的是文字版2021年上半年軟考網絡工程師考試上午真題及答案解析71-75題。

●Network Addres Translation(NAT) is an Internet standard that enbles a local-area network to use one set of IP addresses for internet traffic and another set of (71) IP addresses for external traffic. The main use of NAT is to limit the number of public IP addresses that an organization or company must use, for both economy and (72) purposes. NAT remaps an IP address space into another by modifying network address information in the (73) header of packets while they are in transit across a traffic routing device. It has become an essential tool in conserving global address space in the face of (74) address exhaustion. When a packet traverses outside the local network, NAT converts the private IP address to a public IP address. If NAT runs out of public addresses，the packets will be dropped and (75)"host unreachable"packets will be sent.

(71) A. local

B. private

c. public

D. dynamic

(72) A. political

B. fairness

c. efficiency

D. security

(73) A.MAC

B. IP

c.TCP

D. UDP

(74) A. IPv4

B. IPv6

c. MAC

D. logical

(75) A. BGP

B. IGMP

c. ICMP

D. SNMP