Lecture 3/4 - IP Addressing Scheme

Question 1

What is an IP Address?

Answer 1

An IP Address is an address that uniquely identifies a node on an IP network on the public internet.

Question 2

What is the format of an IP Address? [2]

Answer 2

• An IP Address is typically represented in dotted-decimal notation.
• It consists of 4 numbers within a predefined ranged, separated by a period:
  X.Y.Y.Y
  where X indicates the class
  and Y can be between 1 - 254

Question 3

Differentiate between Unicast [1], Multicast [1] and Broadcast [2]

Answer 3

• In unicast communication, packets are sent from a sender to a single receiver on the system
• In Multicast communication, packets are sent from a sender to a group of receiver on the network, but not to all
• In Broadcast communication packets are transmitted from a sender to all receivers within a subnet
• Broadcast packets are not forwarded by routers.

Question 4

Discuss about the classes of IP Addresses [A2, B2, C2, D1, E1]

Answer 4

• Class A is intended for very large networks with a large number of nodes
• The MSB is 0, hence X: 1-126
• Class B is intended for medium-sized networks supporting a large number of nodes
• The MSB has value 10, hence X: 128-191
• Class C is intended for small networks with a few nodes
• The MSB has value 110, hence X: 192-223
• Class D addresses are used for multicasting and are known as Multicasting Addresses.
• Class E addresses are reserved for future use, experimental and research purposes.

Question 5

What is 127.0.0.1 used for? [3]

Answer 5

127.0.0.1 is reserved for loopback.

It is a special address that offers a means to test the functioning of NICs, their drivers and software WITHOUT REQUIRING A PHYSICAL CONNECTION TO A NETWORK.

Packets sent to the loopback address are intercepted and shipped back to the sending application.

Question 6

Define Network Id (NID) [2]

Answer 6

• It is the first part of an IP address

* It uniquely identifies a network segment (subnet) within a network

Question 7

Define Host Id (HID) [2]

Answer 7

• It is the last part of an IP address

* It uniquely identifies a device(host) within a subnet

Question 8

Define Broadcast address

Answer 8

It is a special type of IP address that is used for sending packets to all recipients on a subnet

Question 9

Given an IP address, how do you computer the Broadcast address?

Answer 9

1. Set the Host Bits to 255

Question 10

Define Subnet mask

Answer 10

It is a number that defines a range of IP addresses that can be used in a subnet

Question 11

Given an IP address, how do you obtain the Default Subnet Mask? [2]

Answer 11

1. Set the Network ID to 255

2. Set the Host ID to 0

Question 12

Define Network Address [2]

Answer 12

• A network address is a logical address that uniquely identifies a network segment (subnet)
• Nodes having the same network address can communicate with each other

Question 13

Given a set of IP Addresses and their respective subnet masks, how to you determine if the nodes can communicate?

Answer 13

1. Compute the Network Address of each node

2. Devices with the same network address can communicate

Question 14

Given a Non-Default Subnet mask, how do you determine the Host Bits and Last Bits?

Answer 14

The host bit is the number of CONTINOUS 1s in the Subnet ID

The number of 0s in the Subnet ID gives the Last Bits

Question 15

Given the Host Bits (HB) and Last Bits (LB) how do you calculate the (1) number of subnets and (2) number of devices per subnets?

Answer 15

1. # of Subnets = 2^(HB) - 2

2. # of Device / Subnet = 2^(LB) -2

Question 16

Given an IP address and its corresponding Non Default Subnet Mask, can you find the range of IP addresses?

Answer 16

Yes :)