Networks practice questions.

A college owns every cable and switch that joins the three buildings standing on its single campus. How should this network be classified?

• A WAN, because three separate buildings have to be linked together
• A MAN, because the network reaches beyond a single street address
• A LAN, because it is one site with self-owned links
• A PAN, because a single organisation controls every device

Answer: A LAN, because it is one site with self-owned links

A LAN is defined by a single site and by the organisation owning the connecting infrastructure, not by how many buildings or machines are involved. A WAN begins where the links have to be leased from a carrier that crosses public land.

Every computer in a house is given an address such as 192.168.0.14, yet a web server on the internet sees a single address for the whole household. Which statement explains this correctly?

• Each computer sends its own address to the web server, which keeps a list of them all
• The addresses inside the house are private, so the router substitutes its public one
• A private address is routed across the internet in exactly the same way as a public one
• Every computer in the house shares the single MAC address that the router hands out to it

Answer: The addresses inside the house are private, so the router substitutes its public one

Addresses in ranges such as 192.168.x.x are reserved for use inside a private network and are never routed across the internet, so the router substitutes its own public address and remembers which reply belongs to which machine. A MAC address plays no part in this: it identifies hardware on one link, not a household.

Which statement describes the internet most accurately?

• The collection of web pages and of the links that join them to one another
• A worldwide set of networks joined together and using shared protocols
• A single very large network owned and operated by one commercial organisation
• The software a browser uses to display pages that are stored on a remote server

Answer: A worldwide set of networks joined together and using shared protocols

The internet is infrastructure, a network of networks whose members agree on one family of protocols; the web is only one of the services carried on it. Treating the two as the same thing makes email, a video call or a software update impossible to place.

In the TCP/IP model, which layer adds the source and destination IP addresses and decides by which route a packet leaves the host?

• The internet layer
• The transport layer
• The application layer
• The network access layer

Answer: The internet layer

The internet layer works with IP addresses and routing, while the transport layer only labels the conversation with port numbers and, in TCP, repairs losses. Placing addressing in the transport layer leaves nothing for a router to examine.

A packet leaves a laptop and crosses two routers before it reaches a distant web server. Which statement about the addresses it carries is correct?

• The MAC address is carried unchanged from end to end while the IP address is rewritten at every router
• Both of the addresses are replaced by every router that handles the packet
• The MAC address is the value used to choose a path across the internet
• The IP address stays the same end to end while the MAC address changes on each link

Answer: The IP address stays the same end to end while the MAC address changes on each link

The IP address identifies the final destination and is what routers use to choose a path, while the MAC address only identifies the next device on the current link and is replaced hop by hop. Treating a MAC address as routable across the internet is a frequent error.

Two companies design wireless adapters independently of each other, yet the finished adapters can exchange data reliably. Which factor makes this possible?

• Both adapters run exactly the same operating system software internally
• Both adapters were manufactured and tested in the same country
• Both were built to one published standard and so implement the same protocol
• Both adapters use an identical physical connector on the same kind of circuit board

Answer: Both were built to one published standard and so implement the same protocol

A published standard fixes what has to be implemented, so two independent designs end up following the same protocol and can interoperate without sharing any code. Identical hardware or identical software is neither necessary nor sufficient for that.