Learning Guide 3: Web Server Management and Services
Federal TVET Institute
Department of Information Communication Technology
Master of ICT Teachers Education
Learning Guide 3: Web Server
Management and Services
(IIS, FTP, DHCP and DNS)
Information Sheet 3.2: Implementing DNS and
DHCP Server
Dr. Patrick D. Cerna (Associate Professor)
Information Sheet 3.2: DNS/DHCP by: Dr. Patrick D. Cerna Page 42
Learning Guide 3: Web Server Management and Services
3.3 What is DNS?
3.3.1 Overview of DNS Server
The Domain Name System (DNS) is a hierarchical distributed naming system for computers,
services, or any resource connected to the Internet or a private network. It associates various
information with domain names assigned to each of the participating entities. Most prominently,
it translates domain names, which can be easily memorized by humans, to the numerical IP
addresses needed for the purpose of computer services and devices worldwide. The Domain
Name System is an essential component of the functionality of most Internet services.
The Domain Name System (DNS) is a standard technology for managing public names of Web
sites and other Internet domains. DNS technology allows you to type names into your Web
browser like www.tveti.edu.et and your computer to automatically find that address on the
Internet. A key element of the DNS is a worldwide collection of DNS servers.
A DNS server is any computer registered to join the Domain Name System. A DNS server runs
special-purpose networking software, features a public IP address, and contains a database of
network names and addresses for other Internet hosts
3.3.1 How DNS Works
The DNS is a distributed system, meaning that only the 13 root servers contain the complete
database of names and addresses. All other DNS servers are installed at lower levels of the
hierarchy and maintain only certain pieces of the overall database.
Most lower level DNS servers are owned by businesses or Internet Service Providers (ISPs). For
example, Google maintains various DNS servers around the world that manage the google.com,
google.co.uk, and other domains. Your ISP also maintains DNS servers as part of your Internet
connection setup.
Information Sheet 3.2: DNS/DHCP by: Dr. Patrick D. Cerna Page 43
Learning Guide 3: Web Server Management and Services
DNS networking is based on the client / server architecture. Your Web browser functions as a
DNS client (also called DNS resolver) and issues requests to your Internet provider's DNS
servers when navigating between Web sites.
When a DNS server receives a request not in its database (such as a geographically distant or
rarely visited Web site), it temporarily transforms from a server to a DNS client. The server
automatically passes that request to another DNS server or up to the next higher level in the DNS
hierarchy as needed. Eventually the request arrives at a server that has the matching name and IP
address in its database (all the way to the root level if necessary), and the response flows back
through the chain of DNS servers to your client.
3.3.3 DNS Servers and Home Networking
Computers on your home network locate a DNS server through their Internet connection setup
properties. Providers give their customers the public IP address(es) of primary and backup DNS
servers. You can find the current IP addresses of your DNS server configuration via several
methods:
on the configuration screens of a home network router
on the TCP/IP connection properties screens in Windows Control Panel (if configured via that
method)
from ipconfig (windows) / ifconfig (linux) or similar command line utility
DNS Server: An Example
If you've ever used the Internet, it's a good bet that you've used the Domain Name System,
or DNS, even without realizing it. DNS is a protocol within the set of standards for how
computers exchange data on the Internet and on many private networks, known as the TCP/IP
protocol suite. Its basic job is to turn a user-friendly domain name like "tveti.edu.et" into
an Internet Protocol (IP) address like 70.42.251.42 that computers use to identify each other on
the network. It's like your computer's GPS for the Internet.
Information Sheet 3.2: DNS/DHCP by: Dr. Patrick D. Cerna Page 44
Learning Guide 3: Web Server Management and Services
Computers and other network devices on the Internet use an IP address to route your request to
the site you're trying to reach. This is similar to dialing a phone number to connect to the person
you're trying to call. Thanks to DNS, though, you don't have to keep your own address book of
IP addresses. Instead, you just connect through a domain name server, also called a DNS
server or name server, which manages a massive database that maps domain names to IP
addresses.
Whether you're accessing a Web site or sending e-mail, your computer uses a DNS server to look
up the domain name you're trying to access. The proper term for this process is DNS name
resolution, and you would say that the DNS server resolves the domain name to the IP address.
For example, when you enter "http://www.tveti.edu.et" in your browser, part of the network
connection includes resolving the domain name "tveti.edu.et" into an IP address, like
70.42.251.42, for TVET Institute’s Web servers.
You can always bypass a DNS lookup by entering 70.42.251.42 directly in your browser (give it
a try). However, you're probably more likely to remember "Tveti.edu.et" when you want to
return later. In addition, a Web site's IP address can change over time, and some sites associate
multiple IP addresses with a single domain name.
Without DNS servers, the Internet would shut down very quickly. But how does your computer
know what DNS server to use? Typically, when you connect to your home network, Internet
service provider (ISP) or WiFi network, the modem or router that assigns your computer's
network address also sends some important network configuration information to your computer
or mobile device. That configuration includes one or more DNS servers that the device should
use when translating DNS names to IP address.
So far, you've read about some important DNS basics. The rest of this article dives deeper into
domain name servers and name resolution. It even includes an introduction to managing your
own DNS server. Let's start by looking at how IP addresses are structured and how that's
important to the name resolution process.
Information Sheet 3.2: DNS/DHCP by: Dr. Patrick D. Cerna Page 45
Learning Guide 3: Web Server Management and Services
Figure 3.5 – DNS Server
3.4 What is DHCP?
3.4.1 Overview of DHCP Server
Computer networks can be of any form like a LAN, WAN etc. If you are connected to a local
LAN or an internet connection, the IP addresses form the basis of communication over computer
networks. An IP address is the identity of a host or a computer device while connected to any
network.
The Dynamic Host Configuration Protocol (DHCP) is a standardized network protocol used
on Internet Protocol (IP) networks for dynamically distributing network configuration
parameters, such as IP addresses for interfaces and services. With DHCP, computers request IP
addresses and networking parameters automatically from a DHCP server, reducing the need for
a network administratoror a user to configure these settings manually.
Information Sheet 3.2: DNS/DHCP by: Dr. Patrick D. Cerna Page 46
Learning Guide 3: Web Server Management and Services
Dynamic Host Configuration Protocol is used by computers for requesting Internet Protocol
parameters, such as an IP address from a network server. The protocol operates based on
the client-server model. DHCP is very common in all modern networks ranging in size
from home networks to large campus networks and regional Internet service provider networks.
Most residential network routers receive a globally unique IP address within the provider
network. Within a local network, DHCP assigns a local IP address to devices connected to the
local network.
DHCP (Dynamic Host Configuration Protocol) Server simplifies the management of IP address
configuration by automating address configuration for network clients. All computers that
participate on TCP/IP networks or the Internet need to have IP addresses assigned to them and
have other IP information configured. IP addresses allow computers and other network hosts to
communicate with other computers or hosts on the network.
3.4.2 How DHCP Server Works?
Some of the additional information needed by network clients may include a subnet mask,
default gateway and DNS server information. This information is needed in order for the
computer to do things such as send data outside the network and resolve host names to IP
addresses. Rather than manually inputting all of this information on each client, DHCP can do
this for you automatically once its setup on the DHCP server.
In order for DHCP to work you need to have a device acting as a DCHP server. This device can
be a computer, router or other type of network device. The DHCP server is configured with a
range or ranges of IP addresses that can be used to give to clients that request one. It can also be
configured with other network parameters as stated earlier.
For a client to be able to obtain information from a DHCP server it must be DHCP enabled.
When it is configured this way then it will look for a DHCP server when it starts up
Information Sheet 3.2: DNS/DHCP by: Dr. Patrick D. Cerna Page 47
Learning Guide 3: Web Server Management and Services
Figure 3.6 – DHCP Server
=================================END===============================
References:
1. “Principles of Network and System Administration” (2nod Edition), John Wiley and Sons
Ltd, Mark Burgess, 2004.
2. “Essential System Administration”, 3rd Edition, O’Reilly and Associates Inc., Len
Frisch, 2003.
3. “Running Linux”, (5th Edition), O’Reilly and Associates Inc., Matthias Kalle Dalheimer
and Matt Welsh, 2007.
4. http://en.wikipedia.org/wiki/Domain_Name_System
5. https://www.isc.org/downloads/dhcp/
Information Sheet 3.2: DNS/DHCP by: Dr. Patrick D. Cerna Page 48
