R ( D)

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26 Οκτ 2013 (πριν από 4 χρόνια και 13 μέρες)

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R
EVIEW

(
NETWORK

D
ESIGN
)

1

1. List some of the major tasks that
should be accomplished in the design
phase.


The following are some of the major tasks
commonly accomplished in the design phase.


First, the designer(s) will investigate the
requirements for the future network.


Develop a logical network model which should
include the specifications for the protocols,
applications, network media, and network
devices.


Develop an IP addressing and routing strategy.


The designer needs to develop a security policy.


Based on the logical network, the designer will
develop a plan for the physical implementation of
the network.


2

2.

What are the layers in the Cisco
hierarchical network design
model?

Describe the role of each layer in
the hierarchical network model.
What are three roles of the
hierarchical model’s core layer?

What are some of the benefits
provided by the Cisco Network
Architectures?


3


The Cisco hierarchical network design model has
three layers, the core layer, the distribution layer,
and the access layer.




The role of each layer in the hierarchical network
model is as follows:


Core Layer: connects Distribution Layer devices,
provides high
-
speed, backbone transport


Distribution Layer: interconnects smaller LANs


Access Layer: provides connections for hosts and
end devices



Three roles of core layer


Provide fast and efficient data transport


Provide maximum availability and reliability


Implement scalable routing protocols


Functionality, scalability, availability, performance,
manageability, and efficiency



4

3. To determine how IP addresses
should be assigned, what are the
decisions a designer has to make?

The designer should make decisions on the following options.


Use either public IP addresses or private IP addresses for
hosts and subnets.


Make decisions on the number of subnets and the number
of hosts in each subnet.


Choose to use either classless IP addresses or
classful

IP
addresses.


Determine whether to use a hierarchical routing
infrastructure or a flat routing infrastructure.


Decide whether to use the variable length subnet mask.


Determine whether to use
supernets
.


Decide if a host should be assigned a static IP address or
automatically assigned a dynamic IP address.


Reserve a range of static IP addresses for servers and
routers.

5

4. Who should be included in
creating a security policy?


The security policy is created by a team
that consists of an organization’s
administrators, network managers, and
user representatives

6

5. What are the prefix and suffix
of an IP address?


In IPv4, the 32 binary bits are divided
into two parts. The first part is called the
prefix which is used to identify the
networks. The second part is called the
suffix which is used to identify the hosts
in a network.

7

6. What are the improvements of
IPv6 over IPv4?

The following are some of the improvements.



IPv6 supports a large number of IP addresses.


IPv6 has a flexible header structure that can
minimize header overhead.


IPv6 supports the hierarchical addressing and
routing infrastructure to reduce the load on backbone
routers.


IPv6 does not support broadcasting. Instead, it
supports the more efficient
unicast
, multicast, and
anycast
.


IPv6 can create a high quality path between the
sender and the receiver for transmitting multimedia
content.


IPv6 has the built
-
in encryption service for data
security.

8

7
. M
ATCH

THE

PPDIOO
NETWORK

LIFECYCLE

PHASES

WITH

THEIR

CORRECT

DESCRIPTIONS
.

9

Prepare phase: 5


Plan phase: 2


Design phase: 4


Implement phase:
1


Operate phase: 6


Optimize phase: 3

1.
The network is built and verified based
on design requirements.

2.
The network requirements, where the
network will be installed, and who will
require network services are identified.

3.
Includes the identification and resolving
of network problems, proactively.

4.
A design is proposed based on the initial
network requirements along with
additional data.

5.
The organizational requirements,
development of network strategy, and
proposed high
-
level conceptual
architecture are completed.

6.
Includes the maintenance of the network
and day
-
to
-
day activities.


8. What are the three basic steps of
the design methodology when using
the PPDIOO lifecycle framework?


Identify customer requirements,
characterize the existing network and
sites, design the network topology and
solutions

10

9. What steps are involved in
identifying customer design
requirements?


Identifying network applications and
network services, defining organizational
goals, organizational constraints,
technical goals, assess technical
constraints

11

10. List some common
organizational constraints.


Budget, availability of personnel, policies,
schedule availability

12

11. What types of redundancies can
be implemented in networking?


Device redundancy, including card and
port redundancy


Redundant physical connections to
workstations and servers


Route redundancy


Link redundancy

13

12. A corporate network is spread
over four floors. Each floor has a
Layer 2 switch and more than one
VLAN. One connection from each
floor leads to the basement, where
all WAN connections are
terminated and all servers are
located. Traffic between VLANs is
essential. What type of device
should be used in the basement?

14

A multilayer switch should be used as the
building distribution layer in the basement
to route between the VLANs, route to the
WANs, and take advantage of the
intelligent network services, such as
QoS

and traffic filtering, which must be
supported at the distribution layer.


15

13. Which of the possible routing
protocols are recommended to be
used at the campus core?


EIGRP or OSPF


16

14. What is Hierarchical Network
Design? What are its advantages over
Flat Networks


In networking, a hierarchical design is used to group devices into
multiple networks. The networks are organized in a layered
approach. The hierarchical design model has three basic layers:


Core Layer
-

Connects Distribution Layer devices


Distribution Layer
-

Interconnects the smaller local networks


Access Layer
-

Provides connectivity for network hosts and end
devices



Advantages:


Hierarchical networks have advantages over flat network designs.
The benefit of dividing a flat network into smaller, more
manageable blocks is that local traffic remains local. Only traffic
that is destined for other networks is moved to a higher layer.


Layer 2 devices in a flat network provide little opportunity to
control broadcasts or to filter undesirable traffic. As more devices
and applications are added to a flat network, response times
degrade until the network becomes unusable.


17

15. When designing firewall rule sets
and Access Control Lists (ACLs,
which users or system processes are
granted access to objects, as well as
what operations are allowed on given
objects) for a client, what is the
general policy concerning
unauthorized traffic? Why?


When designing firewall rule sets and ACLs
for a client, the general rule is to deny all
traffic that is either not specifically
authorized or is not in response to a
permitted inquiry. This is done to ensure that
only authorized traffic is permitted.


18

16. You are the network designer for
XYZ Company. You plan an IP
utilities and tools to perform
connectivity and reach ability tests to
validate the LAN technologies and
devices. What two utilities or tools
could you use?


Ping and
traceroute


Many others;
netstat
,
nslookup
,
arp
,
telnet can test connectivity and display
information from the PC.


19

17. You are the network designer for
XYZ Company. Your client needs a
secure way of transmitting
information across a shared network.
What would you recommend they
incorporate into the network design?


VPN would be beneficial in providing
secure transmission of information. A
VPN is an extension of the internal
private network. VPNs transmit
information securely across shared or
public networks, like the internet.

20

18. You are the network designer for
XYZ Company. Your client needs a
Mean Time Between Failure (MTBF)
for a network is 4000 hours. The
availability goal is 99.98%. Compute
Mean Time to Repair (MTTR).


MTTR = 1 hour, the network failure
should be fix
within 0.8 hour
.


21

19. A network design customer has a
goal of 99.8% uptime. How much
downtime will be permitted in hours
per week? How much downtime will
be permitted in minutes per day?


Uptime = 167.664, downtime =
168
-
167.664 = 0.336 hour


22

Uptime = 1437.12 minutes, downtime =
24
×
60
-
1437.12 = 2.88minute

20. A packet switch has 5 users, each
offering packets at a rate of 10
packets per second

The average length of the packets is
1,024 bits. The packet switch needs to
transmit this data over a 56
-
Kbps
WAN circuit. What is the average
number of packets in the queue? If
the number of the user increased to
100. The packet rate per user keeps
the same. WAN circuit changed to T1
(1.544
-
Mbps), what is the average
number of packets in the queue?

23

Queue depth =
utilisation
/(1
-

utilisation
)



Load = 5 x 10 x 1,024 = 51,200 bps


Utilization = 51,200/56,000 = 91.4%


Average number of packets in queue =
(0.914)/(1
-
0.914) = 10.63 packets





Utilization = 1024000/1544000 = 66.3%


Average number of packets in queue =
(0.663)/(1
-
0.663) = 2 packets

24

Scenario one

Refer to Figure, design the addressing
scheme for the network.

Ensure that you include the following:

Address the network using the private network
10.0.0.0. Design the addressing scheme so that it
allows for the summarization of addresses between
areas. Show the summarization that you allocate,
and explain your reasons for your choices.

Area 0 is using a prefix of 28 bits within the area.

Area 2 is using a prefix of 22 bits within the area.

Area 3 is using a prefix of 24 bits within the area.

Area 4 is using a prefix of 30 bits for the serial
connections. It is using a 28
-
bit prefix for the
connections to the Ethernet routers. Do not include
the subnets attached to the LANs in Area 4.

25

26

27

Ar
ea

Subnet/Pref
ix

Subnet Range

Reasons

0

10.0.0.0/28

10.0.0.16 to
10.0.255.224

The use of the zeros in the second octet is an easy reminder that you
are in Area 0. Because Area 0 is a transit area, it will be small. The
addressing within the area would be allocated the prefix of 28 bits,
allowing the range of SUBNETS shown. The number of hosts on each
of these subnets would be 15.

2

10.2.0.0/22

10.2.0.0 to
10.2.252.0

Again, the private addressing of 10.0.0.0 as a Class A address is so
large that full use may be made of the documentation advantages of
the addressing scheme. The second octet allows Area 2 to be
identified. The prefix of 22 bits is used within the area. This allows
1022 hosts on each network, which is good for further VLSM and
VLANs in switched environments.

3

10.3.0.0/24

10.3.0.0 to
10.3.255.0

The second octet identifies the area. Within the area, a 24
-
bit prefix is
used to address the LANs.

4

10.4.0.0/28

. . .

10.4.100.0/3
0

Ethernet:
10.4.0.16 to
10.4.255.240

Serial:
10.4.100.0 to
10.4.100.250

The second octet identifies the area. Within the area, a 30
-
bit mask is
used to identify the serial links on which only two addresses are
needed. The subnet 10.4.100.0 was chosen as the subnet to sub
-
subnet
for the serial links simply to ease troubleshooting

all serial links in
the company in any area would be assigned the third octet of 100. A
28
-
bit mask was chosen for the Ethernet connections to allow the
creation of many subnets.

Scenario two


Mr. Robertson, the IT director at Pearland Hospital, is responsible for
managing the network. Mr. Robertson has requested your help in
proposing a network solution that will meet the hospital’s
requirements. The hospital is growing, and the management has
released funds for network improvements.



The medical staff would like to be able to access medical systems using
laptops from any of the patient rooms. Doctors and nurses should be
able to access patient medical records, x
-
rays, prescriptions, and recent
patient information. Mr. Robertson purchased new servers and placed
them in the data
center
. The wireless LAN (WLAN) has approximately
30 laptops, and about 15 more are due in six months. The servers must
have high availability.



Patient rooms are on
floors

6 through 10 of the hospital building.
Doctors should be able to roam and access the network from any of the
floors
. A radio
-
frequency report mentions that a single access point
located in each communication closet can reach all the rooms on each
floor
. The current network has ten segments that reach a single router
that also serves the Internet. The router is running Routing
Information Protocol Version 1 (RIPv1). The back
-
end new servers are
located in the same segment as those used on
floor

1. Mr. Robertson
mentions that users have complained of slow access to the servers. He
also hands you a table with current IP addresses

28

C
URRENT

IP A
DDRESSES

Floor

Servers

Clients

IP

Network

1

15

40

200.100.1.0/24

2

0

43

200.100.2.0/24

3

0

39

200.100.3.0/24

4

0

42

200.100.4.0/24

5

0

17

200.100.5.0/24

6

0

15

200.100.6.0/24

7

0

14

200.100.7.0/24

8

0

20

200.100.8.0/24

9

0

18

200.100.9.0/24

10

0

15

200.100.10.0/24

29


Mr. Robertson would like a proposal to
upgrade the network with fast switches
and to provide faster access to the servers.
The proposal should also cover secure
WLAN access on floors 6 through 10.
Include an IP addressing scheme that
reduces the number of Class C networks
the hospital uses. Mr. Robertson wants to
reduce the number of networks leased
from the Internet service provider (ISP).


Answer questions

1.

What are Pearland Hospital’s business requirements?

2.

Are there any business
-
cost constraints?

3.

What are the network’s technical requirements?

4.

What are the network’s technical constraints?

5.

Prepare a logical diagram of the current network.

6.

Does the hospital use IP addresses effectively?

7.

What would you recommend to improve the switching
speed between
floors
?

8.

Based on the number of servers and clients provided,
what IP addressing scheme would you propose?

9.

What routing protocols would you recommend?

10.
What solution would you recommend for WLAN
access and the network upgrade?

31