Final Exam
Started: Aug 13 at 9:33pm
Quiz Instructions
This final exam has multiple choice, short answer, fill in the blanks and numerical
problem questions worth a total of 101 points.
Students will not always receive the same questions. Students will see the answers to
the same question in different orders.
You have 180 minutes. Starting any time from 7PM to 10PM PST. Your final should
be saved automatically when time runs out. You have been given 2 attempts at the
exam. The second attempt should be used only if you are disconnected during the
exam.
You will be asked to upload a file containing a diagram, another file containing some
tables. I have provided a separate canvas activity for you to upload each file to. The
canvas activity will be open till 1AM but you will be expected to submit your files within
10 minutes of finishing your exam (time running out)
This quiz is open book and open web.
You MAY NOT consult or discuss the exam with your classmates or any other
person or online service
You may use any course material, Please answer all questions in your own words.
Points will not be given for copying from the slides.
You may use any online material to help you, but you should not directly copy such
material unless you acknowledge the source and extent of the material you are
directly copying.
3 ptsQuestion 1
Consider aggregation in CIDR.
Company X has has 4 networks. Company X’s network allocation is the smallest
allocation that could include all 3 of its networks. Company X’s allocation excludes the
addresses used by Company Y. Company X’s three networks are
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122.233.32.0/21 122.233.48.0/22 122..233.64.0/20
What is the single aggregated network that the ISP provider can use in its routing table
to assure that all traffic for Company X goes to the router for Company X? Show your
intermediate calculations
3 ptsQuestion 2
None of the other answers are true
When using MLDv1 each host will send 1 response message for each of the
multicast groups it belongs to
When using MLDv2 a host will almost always send 1 response message
When using MLDv2 all multicast addresses the host is a member of are
included in one or more responses
When MLDv2 is used the response message is dropped if a response
Which of the following statement about MLD is true?
message from another host is seen before the timer expires
10 ptsQuestion 3
Consider IGMPv3. Answer each of the following questions. Each answer should contain
approximately one concept for each point.
A. [2 points] Does a host join a multicast group if it wishes to send traffic to the
multicast group? Does a host join an IGMP group if it wishes to receive traffic
being sent to the address of the multicast group?
B. [3 points] Assume a host wishes to join a multicast group. Give a brief step by
step description of how the host joins the group. Mention the type of message
sent and the host that sent it, the address that message was sent to and the
action taken by the receiver of the message
C. [3 points] Do IGMP packets leave the local network on which they are
generated? If so why and where do they travel to? If not how are they prevented
from being forwarded outside the local network and why would they be
prevented from leaving the local network?
D. [2 points] When a host that is a member of 4 multicast groups receives a general
query from the multicast router how many reply packets does it create? Describe
the important contents of the IGMP report or reports.
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10 ptsQuestion 4
Consider the DNS protocol
In this problem the virtual lab was used to capture the packets sent when the command
dig october +search was executed. The packets captured are shown below. Part of the
/etc/resolv.conf file is also shown.
A. [2 points] From the packets captured infer the search line in the file /etc/resolv.conf
on the host where the packets were captured.
B. [6 points] Explain how the resolver dig uses the search line to complete the dns
domain names (that are not FQDNs) and search for october. Give a step by step
description, including how each query and response relates to the search line in the
/etc/resolv.conf file.
C. [2 points] What would happen if no answer was found by the query to nameserver
fdd0:8184:d967::c0a8:64.
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10 ptsQuestion 5
Consider the small IPv6 network illustrated below. Assume the IPv6 global address or
addresses of each of the hosts on this network are allocated using EUI-64 auto-
configuration. Router A and Router B are IPv6 routers. The prefixes these two routers
advertise are given below (Prefix information is taken from the router announcements
made by router A and router B. Auto configuration assigns host B a global address
fdd0:8184:d967:217:21b:2cff:fe3d:4e5f.
A. [1 point] Can an IPv6 interface on a host have more than 1 global IPv6 address?
B. [4 points] Consider the following router announcements from router A and router B.
The router announcements from router A include the following prefix information
_____________________________________________________________________________
ICMPv6 Option (Prefix information)
Type: Prefix information (3)
Length: 32
Prefix Length: 64
Prefix: fdd0:8184:d967:217::
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____________________________________________________________________________
The router announcement from router B include the following prefix information
___________________________________________________________________________
ICMPv6 Option (Prefix information)
Type: Prefix information (3)
Length: 32
Prefix Length: 64
Prefix: Prefix: fdd0:8184:d967:117::
_______________________________________________________________________
If an IPv6 host can have one global address what would the auto configured global
address of host K be? If an IPv6 host can have more than one global address what
global addresses would the auto configured host K have?
C. [5 points] Give a step by step explanation of how you determined one global
address. Indicate what data you used to derive the address and how you used that
data. The Ethernet address of each host is shown
20 ptsQuestion 6
For this question you will be asked to upload two files. The first file should be uploaded
to the separate (outside the quiz in canvas) activity called diagram. The second file
should be uploaded to the separate activity in canvas called tables.
Consider an autonomous system of several networks administered by company A.
Use the following facts about the networks of company A and company B to draw a fully
annotated diagram and to answer the questions after the list of facts.
The network allocation for company A is 212.144.128.0/18 not including
212.144.166.0/23.
Company A has a router RouterA that connects its networks to its ISP. The
connection to the ISP goes through eth2 on router A
Company A is presently using two networks 212.144.160.0/22 (attached to eth0 of
RouterA) and 212.144.176.0/20 (attached to eth1 of RouterA)
Company B has a historic network allocation of 212.144.166.0/23.
Company B has a router RouterB that connects its network to its ISP. The connection
to the ISP goes through eth1 on RouterB.
Company A and Company B are supported by the same ISP
The ISP accesses Company A through gateway 212.1.1.1 through interface eth6
The ISP accesses Company B through gateway 212.1.1.2 through interface eth5
Company A wants to add a third network (within its current allocation) to support
3000 users
a)j [6 points] Draw an annotated diagram of the networks, routers and connections
between them. Label all routers, networks, interfaces and IP addresses that information
is provided for anywhere in this question. Check the provided values in the tables in part
b as well as the list above. The annotated diagram may be drawn by hand or with your
favourite tool. The resulting diagram should be place in a pdf, odt, doc, docx or png file
and submitted the the activity diagram in the final module.
b) [10 points] Make the following tables and fill them in based on the information in all
parts of this problem. You can make copies of the tables in word or some other tool and
submit them in any of the file types listed in part a. The activity you should submit to is
the tables activity in the final module.
Upload
c) [6 points] Company A wants to add a third network (within its current allocation) to
support 3000 users. Where are the possible locations for this new network? Explain how
you determined these locations. Which of the possible locations would you choose?
why?
Choose a File
15 ptsQuestion 7
Below is a diagram of an autonomous system divided into areas. OSPF routing is being
used as the internal routing protocol. Definitions below should be no more than 2-3
sentences.
A. [2 points] Which routers are members of the backbone area?
B. [3 points] Which routers run both OSPF and BGP? Why (be brief)? What is the term
that describes these routers?
C. [1 point] List the stub networks shown in the AS below.
D. [2 points] List the area border routers in the AS below. How many copies of OSPF
are each of these routers running? Give reasons.
E. [7 points] Give a step by step procedure explaining how two routers who have just
established a adjacency relationship synchronize their OSPF databases.
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15 ptsQuestion 8
Consider the ESP protocol (part of IPSec). ESP can be used to encrypt data being sent
from source host A to destination host B. ESP can also be used to authenticate an IP
datagram sent from host A to host B.
a) [10 points] Words have been omitted in the descriptions below. You should choose a
word from the following list to fill in each of the blanks below. Not all words in the list will
be used. Any word in the list may be used more than once.
Each sentence is labeled A, B, … . In the answer box please write the letter for the
sentence the number for the word then the word itself. For example A1 apple, A2 pear
….
WORD LIST
Transport Public B Tunnel encrypted TCP IP
authenticated
trailer AH Packet Data A ESP
Security
Authority Private UDP Original header new
old
Explanation of encryption and authentication for tunnel mode ESP
A. Host A uses the __1___ key of host ___2__ to encrypt the __3___ header, the UDP or
__4___ header, the TCP __5___ and the ESP ____6__.
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B. A new ___1__ header followed by the __2___ header is prepended before the original
IP header. The new header is not encrypted so that the information needed to deliver the
packet can be read by routers. The ___3__ header is not authenticated.
C. Authentication data is constructed using the encrypted information and the ____1___
trailer. Construction of the authentication data uses the ___2____ key of host __3____
D. The authentication data is put into the ___1____ __2____ field and then the datagram
is sent to host .
E. Host B uses the ___1___ key of host ___2__ to check the datagram is authentic. If the
datagram is not authentic it is discarded.
F. Host B uses the ____1__ key of host ___2__ to decrypt the encrypted information G.
Because no other intermediate host has the ___1___ key of host ____2__ no other host
can decrypt and read the data. The data is protected.
b) [5 points] Briefly explain why AH protocol does not function properly if it is used
behind a NAT? You answer should be 6-10 sentences in length.
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15 ptsQuestion 9
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Consider a source sends a 1500 byte IPv6 TCP packet with no expansion headers. The
source sending this packet receives a “packet too big” message that tells it the packet
must pass through a network with an MTU of 1300 bytes. Assume that the source
sending the TCP packets fragments the MTU 1500 IP datagrams to fit through the MTU
1300 network. Also assume the IPv6 IP header is 40 bytes long, the TCP header is 20
bytes long and an IPv6 fragmentation header is 8 bytes long. Using the diagram in file
frag.pdf in the Canvas final module as a reference answer the following questions for
the original IP datagram (Ethernet frame payload) and for each fragment
I. What headers, listed in the order they would occur from left to right would be in
the payload of the Ethernet frame? DO NOT show any details of the quantities
within each header.
II. Give the quantities requested on the diagram and their numerical values. Show
how you calculated the values .
HINT: The algorithm used is the same as for IPv4 except that the fragmentation header
is needed to hold the fragmentation related quantities
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