Institute of Technology, Carlow

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No:157s




Institute of Technology, Carlow

School of Science

Department of Computing & Networking




SUMMER 2006 EXAMINATIONS





Course Code:

CW020





Course Title:

HC in Science in Computer Networking &
Optical Communications




Course Year:

2





Subject:

Networking II







Date:

08/05 PM




Duration:

3 hours





Examiners:

Mr J Fogarty



Dr G B McKiernan





Special Requirements:





Instructions to Candidate:




1.

Write your Name, Course, Course Year and Class Group on your a
nswer book.

2.

Answer any
FOUR

questions
.

3.

All questions carry equal marks. Marks as indicated in brackets.



Question 1

(25 marks)

Answer FIVE parts only. Each carries 5 marks:


i)

Distinguish fully between routed and routing protocols giving exampl
es of each.


ii)

Detail how the Administrative distance and path cost are used in selecting routes to populate the
routing table.


iii)

Routers typically have four types of memory. Briefly describe each of these memory types as they are
used by the router.


iv)

What ar
e Access Control Lists and how are they used?


v)

Describe VLANs outlining the benefits that they provide.


vi)

Distinguish between static and dynamic routes outlining when each might


be used.






Question 2

(25 marks)

Answer all parts


i)

Describe the main feat
ures and operation of Distance Vector routing.

(7 marks)


ii)

Describe the main features and operation of Link State routing.

(7 marks)


iii)

What are routing loops and describe what is meant by time to


convergence.

(3 marks)


iv)

Briefly describe the following techn
iques that attempt to prevent


routing loops:

(8 marks)



Split horizon



Triggered updates



Holddown timers



Count to infinity




Question 3

(25 marks)

Answer all parts


i)

Outline the key characteristics of RIP.

(5 marks)


ii)

Compare and contrast RIPv1 & RIPv2 ou
tlining the advantages and disadvantages of each.



(5 marks)


iii)

Outline the key features of IGRP.

(5 marks)


iv)

Fully describe how OSPF creates, maintains and exchanges routing

(10 marks)


information. In answering this question the following terms should


be explained:



Links & link
-
state



Area



Cost



SPF Algorithm (Dijkstra)



LSA

a link state advertisement.



Adjacencies Database



Link
-
State Database



Forwarding Database



Designated Router/Backup Designated Router






Question 4

(25 marks)

Answer all parts


i)

Explai
n how switches build their MAC tables and make switching

decisions.

(6 marks)


ii)

Fully describe the two switching modes, store
-
and
-
forward and


cut
-
through.

(7 marks)


iii)

What are redundant topologies in a switched network? Illustrate


your answer with a dia
gram.

(3 marks)


iv)

Explain the concept of Broadcast Storms as they affect switches.

(3 marks)


v)

Outline a scenario in which MAC table instability can occur in


a redundant switched network.

(3 marks)


vi)

Briefly describe how the (Spanning Tree Protocol STP) ove
rcomes


the problems described above.

(3 marks)




Question 5

(25 marks)

Answer all parts


i)

Describe the three blocks of private IP addresses and how they are


used.

(3 marks)


ii)

Detail the features and operation of NAT and PAT.

(5 marks)


iii)

Distinguish b
etween classful and classless routing.

(2 marks)


iv)

What is VLSM and why is it used?

(2 marks)


v)

Use VLSM to provide a valid IP address and subnet mask to each


router interface in the diagram below. In your answer, detail the


procedure followed.

(8 marks
)


















vi)

Assuming a company's internal network uses the range of addresses



193.168. 16.0/24
-

193.168.19.0/24, what summary route address and


mask could be advertised on the internet? In your answer, detail the


procedure followed.

(5 mark
s)




West

40 Users

East

27 Users

South

29 Users

The company has been
assigned the Class C
address 192.168.1.0