Computer Networking Basics
Home broadband routers perform NAPT (IP masquerading), a form of NAT (Network Address Translation). What does NAPT make possible?
- ASeveral devices in the home can share one global IP address simultaneously to communicate with the internet, distinguished by port number
- BTraffic between home devices and the internet is encrypted so it cannot be eavesdropped on the way
- CEach device in the home is automatically assigned its own separate global IP address
Show answer and explanation
Answer: A. Several devices in the home can share one global IP address simultaneously to communicate with the internet, distinguished by port number
NAT (Network Address Translation) rewrites the source or destination IP addresses of packets passing through a router. NAPT rewrites port numbers as well as IP addresses and records the mapping between "inside address and port" and "outside port" in a translation table. This lets several devices using private addresses share the router's single global address at the same time. Returning packets are delivered to the right device by looking up the table. It only rewrites addresses and does not encrypt anything. Also, connections started from outside have no entry in the table, so they do not reach inside devices by default; hosting a server inside requires settings such as port forwarding.
- A. Correct. It rewrites port numbers too, so one global address can be shared.
- B. NAPT only rewrites addresses and ports; it does not encrypt.
- C. There is only one global address; each device keeps its private address.