Networking Technologies

This document discusses networking technologies such as subnetting and DHCP. It explains the concept of Variable Length Subnet Masks (VSLM) and how it allows for efficient IP address allocation. It also explores the role of DHCP in automatically assigning network parameters to devices and the use of Automatic Private IP Addressing (APIPA) as a fail-safe mechanism. Additionally, it covers the hybrid system of static and dynamic IP address allocation and the importance of lease time in managing IP address space. Overall, this document provides a comprehensive overview of networking technologies and their significance in network configuration.

Running head: networking technologies 1
Networking Technologies
[Author Name(s), First M. Last, Omit Titles and Degrees]
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Author Note
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QUESTION 1

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IPV4 adresses are limited hence there is use reduce wasteges and maximize utilization of the
adreess space available. This is not achievable by use of simple subnetting technique that
allocates equal number of hosts to each subnet, as aresult a new technique that allocates each
subnet the desired number of addresses is used, it known as Variable Lenngth Subnet Masks
(VSLM) is used. VSLM allows subdivision of an address space into subnets with different
number of IP addresses, therefore it is simple hierarchical subnetting of subnets (Regina
Misevičienė & Julius Kriukas, 2013) To achieve this the networks are arranged in decending
order and subnetting done progressively.
Number of hosts = 2N where N = number of host bits ie bits not borrowed
Usable IP addresses = (2N) - 2 Hence 172.16.0.0/22 has (210)-2 = 1022 addresses
The number of allocated IP addresses must be equal or slightly higher than the number of usable
IP addresses. For the networks with equal number of hosts needed the fixed length subnet mask
applies. Below is a table of the resulting subneted network (Rao & Reddy, 2012)
Subne
t
Host
Addresses
needed (-2)
Addresses
assigned
Network
address
Mask Usabe IP
range
Broadcast
address
A 254 254 172.16.0.0 /24 172.16.0.1-
172.16.0.254
172.16.0.255
B 126 126 172.16.1.0 /25 172.16.1.1-
172.16.1.126
172.16.1.127
C 126 126 172.16.1.128 /25 172.16.1.129-
172.16.1.190
172.16.1.191
D 126 126 172.16.2.0 /25 172.16.2.1-
172.16.1.126
172.16.2.127
E 62 62 172.16.2.128 /26 172.16.2.129 - 172.16.2.191

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172.16.2.190
E 62 62 172.16.2.192 /26 172.16.2.193 -
172.16.2.254
172.16.2.255
G 62 62 172.16.3.0 /26 172.16.3.1 -
172.16.3.62
172.16.3.63
H 62 62 172.16.3.64 /26 172.16.3.65 -
172.16.3.126
172.16.3.127
I 62 62 172.16.3.128 /26 172.16.3.129 -
172.16.3.190
172.16.3.191
J 30 30 172.16.3.192 /27 172.16.3.193 -
172.16.3.222
172.16.3.223
K 30 30 172.16.3.224 /27 172.16.3.225 -
172.16.3.254
172.16.3.255

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QUESTION 2
In Dynamic Host Configuration Protocol (DHCP) enabled networks, a DHCP server is
configured such that the need for the network administrator to manually configure network
parameters for each network host is eliminated, this role is transferred to the DHCP server which
assigns network addresses that are predefined in the local IP address pool. Consequently, the
hosts are configured to be DHCP clients and are therefore able to automatically obtain network
parameters as soon as they boot up (O. Younes, 2017).
In real life, this does not always succeed, this may be due to malfunctioning of the DHCP server
making it unreachable, the occurrence of a network error or even an internal error on the client
device itself. Therefore, a remedy is needed in a case where an attempt by a client to lease an IP
address has failed, this is where Automatic Private IP Addressing (APIPA) Comes in.
Operating Systems such as Windows provision for the Automatic Private IP addressing feature
to allow clients to self-assign themselves IP addresses from Class B private address range of
169.254.0.1 – 169.254.255.254 with a subnet mask of 255.255.0.0 in the event the DHCP server
is unreachable. The significance of APIPA, therefore, is that it provides a DHCP fail-safe
mechanism that protects the devices from fatal failure and allows them to obtain an IPV4 address
even if the DHCP server is not available. After being assigned the APIPA address the clients will
periodically check for the DHCP server and when it's available the APIPA address will be
replaced with a dynamic IP address (Wu, Li, Chen, & An, 2016).
APIPA addresses are limited for use on the local network only, devices configured with the
APIPA addresses can communicate with their APIPA peers within the local network segment but
cannot communicate outside it. Consequently, these devices are unreachable from the outside
network and they can’t communicate to devices in the local network with addresses outside the
APIPA range, for this reason, they can’t log into the domains, print on network printers or access
shared network folders. Unlike the DHCP, APIPA does not provide its clients with the domain
name server and the default gateway hence the devices cannot access the internet (Spinoso,
Leogrande, Risso, Singh, & Sisto, 2018).
Network administrators are advised not to assign addresses from the APIPA range on the local
network as this is likely to result in a network address conflict.

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QUESTION 3
DHCP provides an easier solution in assigning IP address especially in a network with many
hosts but it does this randomly. However, it is desirable that some devices maintain a constant
known IP address in the network. In a DHCP environment devices can maintain the same IP
address if they renew the lease before it expires. However, this is not always the case as other
problem such as network outages may occur hence it is difficult for a DHCP client to maintain a
persistent IP address (O. S. Younes, 2016).
Practically network administrators prefer to use a hybrid system in issuing network address to
hosts. The hybrid system is where a network administrator employs both static and dynamic
address allocation. Example of network devices that may need to be configured with known
permanent IP addresses includes File Servers, Network Printers, and Router Interfaces.
While using the hybrid system in IP address allocation the network administrator must be very
careful to ensure that IP addresses conflict does not occur. An IP address conflict is a scenario
where two or more devices in the same Local Area Network Segment are assigned the same IP
address hence they are not able to communicate. if this occurs it can course errors in the network
and interrupts normal functioning hence it must be avoided at all costs. In ensuring that IP
conflict does not occur the network administrator must guarantee that addresses assigned
statically are not issued by the DHCP server by explicitly excluding them from the local IP
address pool during the DHCP server configuration. Furthermore, the administrator can
configure a device as a DHCP client but force the server to issue it with the same IP address
every time it requests for one. These two operations are made possible by using built-in DHCP
functions know as exclusion and reservation (Vance, 2011).
DHCP Exclusion would remove an IP address or a range of IP addresses from the scope of the
pool of the IP addresses that a DHCP server is allowed to assign. Therefore, an excluded IP
address cannot be assigned dynamically to a host, the only way a device can get these addresses
is when they are statically assigned. Consequently, the function of exclusion is to remove the
range of statically assigned addresses from the DHCP address pool so that they are not assigned
to another device.

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On the other hand, reservation is used to tie a given IP address to a specific device using its
MAC address, therefore, it instructs the DHCP server to issue a particular IP address to specified
network devices every time it requests an IP. Therefore, a reserved IP address cannot be issued to
another device except the one for which it is reserved. The function of reservation is to issue a
constant IP address to the device without having to statically configure it (Tripathi & Hubballi,
2018).
QUESTION THREE
The lease is a DHCP setting that specifies the duration for which a network device is allowed to
use an IP address. When a host first joins the network it requests the DHCP server for a unique
address, the server assigns it an address and specify the amount of time for which it is allowed to
use the address. During this time the address is reserved and cannot be assigned to any other
device. However, in order to continue using the address, the device has to renew its lease time
before it expires or else it will lose the network configuration and has to do the request afresh, to
avoid this devices attempt to renew their lease once they consume half the time.
Lease is a very desirable feature in DHCP when it comes to managing the address space, there
are a limited IP addresses, therefore, a device should be assigned an address for a specific period
time and when it doesn’t renew it for one reason or another it is released back so that it can be
assigned to other deserving clients. If the lease is not implemented or lease period is not set
properly all IP addresses can be held by devices that no longer use them hence preventing others
that want to join the network (Hubballi & Tripathi, 2017).
On Wi-Fi networks, the devices are highly mobile and they will tend to leave the network
frequently and may stay away for a longer time before rejoining. This is not the cases in wired
networks. Bearing this in mind it is therefore recommended that we set shorter lease time for Wi-
Fi network preferably a maximum of 1 hour for hotspots and 8 hours for office guest networks.
This way the devices are forced to renew their lease frequently hence releasing addresses of
those devices that have left the network. Therefore, shorter lease time for Wi-Fi networks is
desirable since it ensures the availability of enough IP address.

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An example is a Wi-Fi hotspot having 100 IP addresses with an average of 200 visitors daily
each taking an average of 30 minutes. If the lease time is set to 24 hours, then it means after 100
visitors no one else will be able to connect to the hotspot until the next day hence the shorter the
lease time the better the performance (Huang & Chu, 2011).

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References
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26, 2019, from https://lazyadmin.nl/home-network/dhcp-lease-time/
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Wu, K., Li, Y., Chen, L., & An, S. (2016). Research of DHCP flooding attack detection
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