Preview

05 - Routing - how it works

 1. Imagine that you are visiting a webpage with an image on it. How does that image get to your computer? Firstly, the image is stored/hosted on a …………………….

  DNS server for images

  web server

  ISP router

  Bridge

 2. A user's computer sends a request to a web server for an image. The request is sent in a ……

  ISP

  packet

  byte sequence

  bit

 3. Think of a packet as a virtual parcel with information in it. The two important bits of information are:

  The head and the body (like an HTML page)

  IP address of the web server (that the image or site is stored on) and the sender's IP address

  The bit sequence and the physical address of the sender

  None of the above

 4. _______________(and devices called switches) direct the packet from the sender's computer to the required web server.

  Routers

  Modems

  ISP servers

  DNS servers

 5. The web server receives the request (for an image) and sends it as packets (routers and switches direct this)

  FALSE

  TRUE

 6. Routers try to …………………………... They might take different routes and might not arrive in the same order they were sent.

  find the fastest possible route for each packet.

  delete all data that comes through it

  None of the above

  block all hacking attempts

 7. Once packets have been received, the information attached to the packet tells the comptuer how (and what order) to put the packets back together again.

  TRUE

  FALSE

 8. The whole process of sending a request and receiving the packets usually takes less than a second!

  FALSE

  TRUE

 9. The router is the only device that sees every message sent by any computer on either of the company's networks

  TRUE

  FALSE

 10. One of the tools a router uses to decide where a packet should go is a configuration table. A configuration table is a collection of information, including:

  Priorities for connections to be used

  Rules for handling both routine and special cases of traffic

  Information on which connections lead to particular groups of addresses

  All of the above

 11. Which of the following 'jobs' does a router do?
Job #1
========
The router ensures that information doesn't go where it's not needed. 
This is crucial for keeping large volumes of data from clogging the connections 
of "innocent bystanders."

Job #2
========
The router makes sure that information does make it to the intended destination.

  Job 1

  Job 2

  Both Jobs 1 and 2

  Neither Job

 12. There are different types of routers. Simple routers (e.g. at home), slightly larger routers(used to connect a small office to the internet) and large routers that…..

  are used to handle data at the major traffic points on the internet

  are usually standalone stystems that have far more in common with super computers than with your office server

  handle millions of packets every second and work to configure the network most efficiently

  All of the above

 13. One of the crucial tasks for any router is knowing when a packet of information stays on its local network. For this, it uses a mechanism called a ……………………………..

  modem

  DNS

  ISP server

  subnet mask

 14. The subnet mask looks like an IP address and usually reads "255.255.255.0. Fill in the blanks in the following excerpt.
This tells the router that all messages with the sender and receiver 
having an address sharing the first three groups of numbers are on the 

.............................

and shouldn't be sent out to another network. Here's an example: 
The computer at address 15.57.31.40 sends a request to the computer at 15.57.31.52. 
The router, which sees all the packets, matches the first three groups in the address 
of both sender and receiver (15.57.31), and keeps the packet on the local network.

  None of the above

  same network

  same modem

  first DNS server

 15. The following excerpt sheds some light on what happens on a busy network. Fill in the blanks.
Depending on the time of day and day of the week, 
some parts of the huge public packet-switched network 
may be busier than others. When this happens, the routers 
that make up this system will communicate with one another 
so that traffic not bound for the crowded area can be sent 
by ................................. 

This lets the network function 
at full capacity without excessively burdening already-busy areas. 

  more congested routes

  configured DNS server routes

  less congested routes

  the most congested route

 16. A router will have at least two …………………………….. one physically connected to one network and the other physically connected to another network

  DNS servers

   network cards (NICs)

  WIFI cables

  Modems

 17. If we have just 3 networks we can connect them in two different ways; one way is to daisy chain them together using only 2 routers. The other way would be to ………………
routingconfiguration_advanced.png

  connect them to the ISP directly

  None of the above

  connect them directly to each other using 3 routers

  connect them to an additional modem

 18. In configuration 1 if router A or B went down …………………………………………………………………. as there is only one path to it.
routingconfiguration_advanced.png

  all the machines from submet A would be able to communicate with subnet C

  no machines from subnet A would be able to communicate with subnet C

  None of the above

  just one machine from subnet A would be able to communicate with subnet C

 19. Routers know the most effective route to use by referring to what is called a metric value. The lowest metric is assumed to be the most efficient.

  FALSE

  TRUE

 20. All network devices that use the TCP/IP protocol have a routing table, even your Windows PC has one. ALL devices use their routing table to…..

  None of the above

  determine which modem is fastest

  determine where to send packets

  decide which internet service provider to use

 21. Without a routing table your PC wouldn’t even be able to communicate with computers on the same subnet

  TRUE

  FALSE

 22. Before sending a packet your PC looks up the destination …………………... in the routing table to determine the best route possible.

  PC MAC address

  packet address

  None of the above

  IP address

 23. If a PC can’t find a matching entry in the routing table it will ……………. It will also……………... if the routing table is wrongly configured.

  send the packets anyway

  fail

  try again

  re-route

 24. When packets take a certain route to their destination they DO NOT have to take the same route back

  TRUE

  FALSE

 25. The main difference between IP routing on the Internet and routing on private networks is how the routing table is built. Private networks tend to use static routing whereas the Internet uses Dynamic Routing.
Static routing is the process of adding IP routing information manually into the routing table.

  TRUE

  FALSE

 26. The act of traversing between one router and another across a network is referred to as a …

  None of the above

  hop

  mop

  routerop

 27. The job of a router is to read the recipient's _____________________ in each packet and forward it on to the recipient via the fastest, least congested route.

  IP address

  ISP server

  DNS address

  Internet MAC address

 28. A router will forward the packet to the next router until the packet reaches its destination. Routers use routing tables to …………………………………… the locations of other network devices.

  store and update

  catch and forward

  find and delete

  delete and ammend

 29. A routing algorithm is used to find the least optimum route.

  FALSE

  TRUE

 30. A common shortest path algorithm used in routing is …..

  None of the above

  Stack Queue algorithm

  Recursive search algorithm

  Dijkstra's algorithm