CS 321 Review Questions on Textbook Topics

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Oct 28, 2013 (4 years and 11 days ago)

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CS 321






Review Questions on Textbook Topics


1)

Which of the following would you recommend for large, complex networks? (Circle all answers that
make good sense.)


a)

OSPF



b)

IGRP



c)

EIGRP


2)

Why is a large maximum hop count helpful (as opposed t
o the small maximum hop count of 15 used
by RIP v1)?


3)

Which of the following can be used to break up broadcast domains?



a)

routers



b)

switches


4)

If a switch receives an incoming frame on E0/2 and the frame's header shows that AA.BB is the
source M
AC address, while 4C.26 is the destination MAC address, what data is recorded in the
switch's forward/filter table? (The MAC addresses have been abbreviated for readability.)


5)

Is it true that all OSPF areas should connect to area 0?


6)

Which of the fo
llowing put network 10.25.4.0/24 into area 0? (Circle all correct answers.)



a)

network 10.25.4.0 0



c)

network 10.25.4.0 255.255.255.0 area 0



d)

network 10.25.4.0 0.0.0.255 area 0


7)

Name one major advantage of switches over hubs.


8)

If yo
u want to be sure that only server A can be plugged into port F0/0 on a Catalyst switch, what is
the best way to ensure this?


9)

Which is the key device for allowing VLANs to communicate with each other?



a)

switch



b)

router



c)

hub


10)

Which of the
following is/are true of VLANs? (Circle all correct answers.)



a)

Dividing a network up into VLANs increases the number of broadcast domains.



b)

Dividing a network up into VLANS decreases the size of broadcast domains.



c)

Dividing a network up into V
LANS increases the size of broadcast domains.


d)

Dividing a network up into VLANS allows you to plug a new user's PC into pretty much any
free port on any switch and still get the user onto any desired VLAN.


e)

Each VLAN should have its own, separate sub
net number.

11)

Consider the fo
llowing network situation, where each of the 3 switches at the bottom forms a separate
VLAN and where we want the VLANs to be able to communicate with each other.




a)

Which interface on which dev
ice must use subinterfaces?



b)

The link between which 2 devices is a trunk line?


c)

Suppose that VLAN2 is the VLAN for switch S2 and that the subnet for VLAN2 is
195.234.27.64/28
. In configuring F0/1 on router R1 we could use:




int f0/1.2



encapsul
ation dot1q 2



ip address ____________________________________


12)

What protocol is typically used to find lots of detailed information about devices directly attached to
a router? (Circle one.)



a)

TCP



b)

CDP



c)

OSPF


13)

Which of the followin
g can be used to resolve symbolic names to IP addresses? (Circle all correct
answers.)



a)

DNS


b)

CDP


c)

host table


14)

What is wrong with the following access list?



access
-
list 20 deny 195.230.64.0 0.0.31.255


access
-
list 20 deny 195.230.192.
0 0.0.63.255


15)

Suppose that you want to blcok packets from 195.200.128.0/19 by using the following entry from
access list 10. Complete this entry.


access
-
list 10 deny _____________________________


R1

S1

R = router

S = switch

H = host

S2

S3

S4


H H H H H H H

F0/1

F0/2

F0/1

F0/3 F0/4

F0/1 F0/1 F
0/1

16)

Which is likely to be less costly for connect
ing your Pittsburgh and Chicago offices?



a)

frame relay


b)

T1 line


17)

Which is likely to give you more bandwidth at all times when connecting your Pittsburgh and
Chicago offices?



a)

frame relay


b)

T1 line


18)

Suppose you negotiate with your provid
er to get frame relay with an access rate of 1.544 Mbps and a
CIR of 512 Kbps.


a)

What is likely to happen if you send a burst of traffic at the rate of 1.8 Mbps?


b)

What is likely to happen if you send a burst of traffic at the rate of 1 Mbps?


c)

What
is likely to happen if you send a burst of traffic at the rate of 256 Kbps?


19)

Consider the situation shown in your text in figure 11.11 on p 539, where each of the routers on the
right has a separate permanent virtual circuit through the frame relay net
work to the single router on
the left.



Should the interface on that single, leftmost router have subinterfaces? If so, how many?


20)

For ISDN, if you want the second B channel to come up when the first channel's load hits about
100%, you would use the
following command at your router. (Circle one.)


a)

dialer load
-
threshold 100 either


b)

dialer load
-
threshold 125 either


c)

dialer load
-
threshold 255 either


21)

You want to be sure that your core switch is selected as the root switch by the s
panning tree
algorithm. Which of the following is a practical way to do this?



a)

Set the priority on the core switch to be 32768, the max possible number.



b)

Set the priority on the core switch to be lower than that of the other switches.



c)

Set the

MAC address of the core switch to be lower than all of the others.



Answers


1)

Which of the following would you recommend for large, complex networks? (Circle all answers that
make good sense.)


a)

OSPF



b)

IGRP



c)

EIGRP



Circle a and c. Both of t
hese provide features that are helpful with larger networks, whereas IGRP is
pretty basic. For example, EIGRP and OSPF provide support for VLSM.


2)

Why is a large maximum hop count helpful (as opposed to the small maximum hop count of 15 used
by RIP v1)?


It allows packets to traverse a large network without being discarded. The max of 15 is often too
small for a large network.


3)

Which of the following can be used to break up broadcast domains?



a)

routers



b)

switches



Answer is a, routers.


4)

If
a switch receives an incoming frame on E0/2 and the frame's header shows that AA.BB is the
source MAC address, while 4C.26 is the destination MAC address, what data is recorded in the
switch's forward/filter table? (The MAC addresses have been abbreviated

for readability.)


The switch places the following interface/MAC address pair into its table:


E0/2

AA.BB

This indicates that the switch now knows that the machine with MAC address AA.BB can be reached
by sending frames out the E0/2 interface.


5)

Is it
true that all OSPF areas should connect to area 0?


Yes, area 0 is the area for the network backbone, to which all other areas should connect.


6)

Which of the following put network 10.25.4.0/24 into area 0? (Circle all correct answers.)



a)

network 10.
25.4.0 0





Incorrect syntax



b)

network 10.25.4.0 255.255.255.0 area 0


Wrong mask



c)

network 10.25.4.0 0.0.0.255 area 0



This works!


7)

Name one major advantage of switches over hubs.


You could certainly say reduced network traffic. This
tends to increase speed, so that is also a good
answer. Better security is also a possibility, since it is harder to sniff traffic on a switch.


8)

If you want to be sure that only server A can send data into port F0/0 on a Catalyst switch, what is the
be
st way to ensure this?



Configure port security on F0/0 of the switch so that it only accepts traffic with server A's MAC
address as the source address.



9)

Which is the key device for allowing VLANs to communicate with each other?



a)

switch



b)

route
r



c)

hub



The answer:

b) router


10)

Which of the following is/are true of VLANs? (Circle all correct answers.)


a)

Dividing a network up into VLANs increases the number of broadcast domains.



b)

Dividing a network up into VLANS decreases the size of

broadcast domains.



c)

Dividing a network up into VLANS increases the size of broadcast domains.


d)

Dividing a network up into VLANS allows you to plug a new user's PC into pretty much any
free port on any switch and still get the user onto any desired
VLAN.


e)

Each VLAN should have its own, separate subnet number.


Answer: a, b, d, e


11)

Consider the following network situation, where each of the 3 switches at the bottom forms a separate
VLAN and where we want the VLANs to be able to communicate with

each other.




a)

Which interface on which device must use subinterfaces? F0/1 on router R1.



b)

The link between which 2 devices is a trunk line? R1 and S1.


c)

Suppose that VLAN2 is the VLAN for switch S2 and that the subn
et for VLAN2 is
195.234.27.64/28
. In configuring F0/1 on router R1 we could use:




int f0/1.2



encapsulation dot1q 2



ip address 195.234.27.65

255.255.255.240


(use any IP address in the subnet)


12)

What protocol is typically used to find lots o
f detailed information about devices directly attached to
a router?

(Circle one.)



a)

TCP



b)

CDP



c)

OSPF



Answer:

b) CDP (Cisco Discovery Protocol does precisely this)


R1

S1

R = router

S = switch

H = host

S2

S3

S4


H H H H H H H

F0/1

F0/2

F0/1

F0/3 F0/4

F0/1 F0/1 F0/1

13)

Which of the following can be used to resolve symbolic names to IP address
es? (Circle all correct
answers.)



a)

DNS


b)

CDP


c)

host table


Answer: a and c


14)

What is wrong with the following access list?



access
-
list 20 deny 195.230.64.0 0.0.31.255


access
-
list 20 deny 195.230.192.0 0.0.63.255



Answer: It is temp
ting to focus on the numbers, but they are reasonable.

(See p493.)

The only thing
wrong with this list is that it denies everything because every access list ends with a default deny any.
We need to have at least one permit entry for this list to be pra
ctical.


15)

Suppose that you want t
o blcok packets from 195.200.128.0/19 by using the following entry from
access list 10. Complete this entry.



Answer:

access
-
list 10 deny 195.200.128.0 0.0.31.255

(See the first entry on p 493.)


16)

Which is likel
y to be less costly for connecting your Pittsburgh and Chicago offices?



a)

frame relay


b)

T1 line




Answer:

a


17)

Which is likely to give you more bandwidth at all times when connecting your Pittsburgh and
Chicago offices?



a)

frame relay


b)

T1 line




Answer:

b


18)

Suppose you negotiate with your provider to get frame relay with an access rate of 1.544 Mbps and a
CIR of 512 Kbps.


a)

What is likely to happen if you send a burst of traffic at the rate of 1.8 Mbps?



It is very likely that only 1.544

Mbps gets through. The excess packets are discarded.


b)

What is likely to happen if you send a burst of traffic at the rate of 1 Mbps?



At least 512 Kbps gets through.
Perhaps a
ll of the 1 Mbps gets through.


c)

What is likely to happen if you send a
burst of traffic at the rate of 256 Kbps?



All 256 Kbps is guaranteed to get through.


19)

Consider the situation shown in your text in figure 11.11 on p 539, where each of the routers on the
right has a separate permanent virtual circuit through the fram
e relay network to the single router on
the left.



Should the interface on that single, leftmost router have subinterfaces? If so, how many?



Answer: Yes, it should have 3, one for each virtual circuit.


20)

For ISDN, if you want the second B channel t
o come up when the first channel's load hits about
100%, you would use the following command at your router. (Circle one.)


a)

dialer load
-
threshold 100 either


b)

dialer load
-
threshold 125 either


c)

dialer load
-
threshold 255 either


Answer:

c


21)

You want to be sure that your core switch is selected as the root switch by the spanning tree
algorithm. Which of the following is a practical way to do this?



a)

Set the priority on the core switch to be 32768, the max possible number.



This is the

default value and is probably the priority on all of the other switches, so this will
not do anything to help.



b)

Set the priority on the core switch to be lower than that of the other switches.



This works well. If one switch has a lower priority num
ber that all of the others, then it will
be chosen as the root switch.



c)

Set the MAC address of the core switch to be lower than all of the others.



The MAC address is installed by the manufacturer. It is impractical to monkey with it or to
try to swa
p hardware so as to get the lowest MAC address where you want it. Use the
priority!