Chapter 4 - Fundamentals of IPv4 Addressing and Routing

Question 1

True or False. All IP addresses in the same group must not be separated from each other by a router.

Answer 1

True

Question 2

True or False. IP addresses separated from each other by a router do not have to be in different groups.

Answer 2

False. IP addresses separated from each other by a router must be in different groups.

Question 3

IP standards subdivide the entire address space into what 5 classes?

Answer 3

Classes A, B, C, D, and E

Question 4

What does DDN stand for?

Answer 4

Dotted decimal notation

Question 5

What address space is allocated to the Class A network?

Answer 5

Approximately one-half with addresses that start with 1-126.

Question 6

What address space is allocated to the Class B network?

Answer 6

Approximately one-fourth with addresses that start with 128-191.

Question 7

What address space is allocated to the Class C network?

Answer 7

Approximately one-eigth with addresses that start with 192-223.

Question 8

What is the Class D network used for and what DDNs are assigned to it?

Answer 8

Used for multicast and it is assigned 224-239.

Question 9

What is the Class E network used for and what DDNs are assigned to it?

Answer 9

Used for experimental and it is assigned 240-255.

Question 10

Which DDN(s) are reserved?

Answer 10

0 and 127

Question 11

How many networks in a Class A network - in the entire world?

Answer 11

126

Question 12

How many networks in a Class B network - in the entire world?

Answer 12

16,384

Question 13

How many networks in a Class C network - in the entire world?

Answer 13

2,097,152

Question 14

How many hosts per Class A network?

Answer 14

16,777,214

Question 15

How many hosts per Class B network?

Answer 15

65,534

Question 16

How many hosts per Class C network?

Answer 16

254

Question 17

What is the network number range for Class A networks?

Answer 17

1.0.0.0 to 126.0.0.0

Question 18

What is the network number range for Class B networks?

Answer 18

128.0.0.0 to 191.255.0.0

Question 19

What is the network number range for Class C networks?

Answer 19

192.0.0.0 to 223.255.255.0

Question 20

What does the term classful IP network refer to?

Answer 20

Any Class A, B, or C network.

Question 21

If the destination IP address is in the same IP subnet as the host, what does the sending host do with the packet?

Answer 21

Sends the packet directly to that destination host.

Question 22

If the destination IP address is NOT in the same IP subnet as the host, what does the sending host do with the packet?

Answer 22

The host sends the packet to the default gateway also known as the default router.

Question 23

What 4 step process does a router go through when it receives a data link frame addressed to that router’s data link address?

Answer 23

Step 1. Use the data link Frame Check Sequence (FCS) field to ensure that the frame had no errors; if errors occurred, discard the frame.
Step 2. Assuming that the frame was not discarded at Step 1, discard the old data link header and trailer, leaving the IP packet.
Step 3. Compare the IP packet’s destination IP address to the routing table, and find the route that best matches the destination address.
Step 4. Encapsulate the IP packet inside a new data link header and trailer, appropriate for the outgoing interface, and forward the frame.

Question 24

What are some goals of a routing protocol?

Answer 24

1) To dynamically learn and fill the routing table with a route to each subnet in the internetwork.
2) If more than one route to a subnet is available, to place the best route in the routing table.
3) To notice when routes in the table are no longer valid, and to remove them from the routing table.
4) If a route is removed from the routing table and another route through another neighboring router is available, to add the route to the routing table.
5) To work quickly when adding new routes or replacing lost routes.
6) To prevent routing loops.

Question 25

What is the time between losing a route and finding a working replacement route called?

Answer 25

Convergence time

Question 26

What 3 general steps do many routing protocols generally use to learn routes?

Answer 26

Step 1. Each router, independent of the routing protocol, adds a route to its routing table for each subnet directly connected to the router.
Step 2. Each router’s routing protocol tells its neighbors about the routes in its routing table, including the directly connected routes, and routes learned from other routers.
Step 3. After learning a new route from a neighbor, the router’s routing protocol adds a route to is IP routing table, with the next-hop router of that route typically being the neighbor from which the route was learned.

Question 27

What does DNS stand for?

Answer 27

Domain Name System

Question 28

What is the purpose of DNS?

Answer 28

Resolves host names such as www.google.com and www.facebook.com to the matching IP address.

Question 29

How do routers treat DNS messages?

Answer 29

Routers treat them like any other IP packet, routing them based on the destination IP address.

Question 30

What does ARP stand for?

Answer 30

Address Resolution Protocol

Question 31

What does ARP do?

Answer 31

A method by which any host or router on a LAN can dynamically learn the MAC address of another IP host or router on the same LAN.

Question 32

What is an ARP request?

Answer 32

A message that asks “if this is your IP address, please reply with your MAC address.”

Question 33

Where does the host or router keep these ARP requests?

Answer 33

In their ARP cache or ARP table.

Question 34

What command can you use to see the contents of the ARP cache or table?

Answer 34

arp -a

Question 35

What is the primary tool used for testing basic network connectivity?

Answer 35

ping

Question 36

What protocol does ping use?

Answer 36

Internet Control Message Protocol - ICMP

Question 37

What are the reserved private IP addresses according to RFC 1918?

Answer 37

Class A Network 10.0.0.0
Class B Network 172.16.0.0 thru 172.31.0.0 (inclusive)
Class C Networks that begin with 192.168