Part 1

1.

What does a router use the network mask in its routing table for?

2.

In a classless IP address explain why the prefix is a critical part of that address.

3.

Assume that in an IPv4 Header, the value of the Header Length field was decimal 12. What is the total length of the Header in bytes?  Explain your answer or show your calculations 

4.

When classful addressing is referred to as “three-level addressing”, briefly explain the three levels referred to.

5.

In the IPv6 protocol, briefly explain in your own words how multiple extensions are indicated.

Part B

1.

The AXES Corporation has obtained a block of IPv4 addresses from an ISP. The block included the address 191.56.125.34/19.

Calculate the number of addresses in this block, the network address, the direct broadcast address, and the range of addresses that would be available for use by hosts.

You may include the calculations with the answer or put the calculations at the end.

The number of addresses available in this block:  

The network address:

The direct broadcast address:  

The range of addresses that can be used by hosts: 

for calculations:

2.

A company has been granted a block of classless addresses which starts at 198.87.24.0/23.  Create the following 4 subnets by calculating the subnet address for each subnet including the prefix.  Create a table to organise your answer.  Show your working in the space provided.

1. 1 subnet with 256 addresses (1 mark correct subnet, 0.5 mark good calcs)
2. 1 subnet with 128 addresses (1 mark correct subnet, 0.5 mark good calcs)
3. 2 subnets with 64 addresses each (1 mark per correct subnet, 0.5 mark good calcs per subnet)

3.

Describe in your own words the processing logic that a router uses in determining whether an incoming packet’s destination is listed in its routing table, and how the packet is treated if it is listed, or if it is not.  Use your own words. 

4.

The section of the Internet in the diagram below shows six networks and four routers, labelled R1, R2, R3 and R4.  Construct the routing table of router R3 by completing the table provided below the diagram.  List the networks in longest mask order.

5.

The classful addressing scheme in IPv4 was very wasteful, leading to the depletion of IPv4 addresses in recent times.  But the impact of the depletion of IPv4 addresses has been minimised due to the use of certain technologies.  Name three major technologies that have minimized or reduced the impact of the depletion of IPv4 addresses and briefly explain how they reduced that impact

Part C

1.

In terms of routing table construction techniques, briefly describe ‘Longest Mask Matching’ in a routing table (1 mark) and the reason for organising the routing table this way

2.

Briefly describe the two transition mechanisms called ‘tunnelling’ and ‘header translation’ in terms of their use during the IPv4-to-IPv6 transition period, including when each scheme would be used. 

3.

The DNS is critical to the operation of the Internet.  Discuss what the DNS does (2 marks), and why it is critical to the operation of the Internet.