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[Approved by AICTE, Govt. of India & AffiliatedtoDr. APY
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Figure 2: PC 1 and PC 2 IP Configuration
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Institute of Technology & Management Department Of Computer Science & Engineering
EXPERIMENT 2
Objective: Configure a DNS server in along 1g network using Cisco Packet Tracer.
Theory:
A Domain Name Service(DNS) server resolves host names into IP addresses. Although we can access
a network host using its IP address, DNS makes it easier by allowing us use domain names which are
easier to remember. For example its much easier to access google website by typing
hitp://www.google.com as compared to typing http://208.117.229.214. In either case, you'll access
google website, but using domain name is obviously easier.
Now, before any host can use a DNS service, we must configure a DNS server first. For example,
‘when you type the URL http://www.google.com in your browser, the host will query the DNS server
for the IP address of http://www.google.com. The DNS server will resolve http://www. google.com
into an IP address then answer back the host with the IP address. An
HTTP server is a web server. It stores web resources that can be accessed by a web client. Your PC’s
browser(a web client) requests for web resources from a web server over the internet. Web resources
are files such as text and images that the server will give to the client on request.
Simulation in Cisco Packet Tracer:
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Figure 1: Network Topology for DNS server (server 1- web server, server 2- DNS server)
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B route - a Open dialogue. The same filters and tools that can be used for natively captured network
data are available for imported files.
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you. It can collect the data, and then analyze it all in one spot. However, desktops are not,
common on
servers, so in many cases, you'll want to capture the network data remotely and then pull
the resulting peap file into Wireshark.
At first launch, Wireshark allows you to either load an existing peap file, or start capturing.
If you elect to capture network traffic, you can optionally specify filter stop are down the
amount of data Wireshark collects. Since its analysis tools are so good, it’s less important
to ensure you surgically identify the data at collection time with Wireshark. If you don’t
specify a filter, Wireshark will simply collect all network data that your selected interface
observes.
Oneofthemostusefultools Wiresharkprovidesistheabilitytofollowastream.lt’sprobablymost
useful to think of a stream as an entire conversation. In the screenshot below we can see a
lot of data has been captured, but what I am most interested in is that Google IP. I can right-
click it and Follow the TCP Stream to see the entire conversation.
96[Approved by AICTE, Go
takes some time to master. A few of the very basic commands involve selecting the network
interface from which to collect data, and writing that data to a file so it can be exported for
analysis elsewhere, The -i and -w switches are used for this.
#tepdump-i eth0-wtepdump_packets
tepdump:listeningon eth0,link-typeEN10MB (Bthemet), capturesize2621-44bytes
C5 packetscaptured
Thisproducesa capturefile:
filetepdump_packets
tepdump_packets:tepdumpeapturefile(little-endian)-
version2.4(Ethemet,capturelength262144)
The standard TCP capture file is apcap file. It is not text so it can only beread by ananalysis
program that knows how to read peap files.
2.WinDump
Most useful open-source tools are eventually cloned to other operating systems. When this
happens, the application is said to have been ported over. Win dump is a port of tep dump
and behaves in very similar ways.
One major difference between WinDump and tepdump is that Windump needs the
WinpCap library installed prior to being able to run WinDump. Despite both WinDump.
and WinpCap being provided by the same maintainer, they are separate downloads.
WinpCap is an actual library that needs to be installed. But, once itis installed, WinDump
is an, exefile that needs no installation so it can just run, That may be something to keep in
mind if you're running a Windows network, You don’t necessarily need WinDump
installed on every machine since you can just copy it over as needed, but you will want
‘WinpCap installed in order to support WinDump.
As with tepdump, WinDump can output network data to the screen for analysis, be filtered
inthesame way,and also writedatato apcap fileforanalysisoffsite.
3.Wireshark
wireshark is probably the next best-known tool in any sysadmin’s toolkit. It can not
onlycapture data, but also provides some advanced analysis tools. Adding to its appeal,
Wiresharkis open source, and has been ported over to almost every server operating system
that exists. Starting life named Etheral, Wireshark now runs everywhere, including a
sastandal one portable app.
If you're analyzing traffic on a server with a desktop installed, Wireshark can do it all for
95@&. GL BASJAS Ser
Experiment No:-15
Objective: - Network packet analysis using tools like Wireshark, tep dump, ete.
Apparatus(Software): Wireshark, tep dump
TCPDUMP:
The fundamental tool of almost all network traffic collection is tep dump. It is an open-
source application that comes installed on almost all Unix-like operating systems. Top
dump is an excellent collection tool and comes complete with a very complex filtering
language.
It simportanttoknowhowtofilterthedataatcollectiontimeinordertoendupwithamanageablech
‘unkofdatatoanalyze.Capturingalldatafromanetworkdeviceonevenamoderatelybusynetwork
cancreate too much data to analyze easily.
In some rare cases, allowing tep dump to output its capture directly to your screen may be
enough to find what you're looking for. For example, in writing this article, T captured
sometratficandnoticedthatmymachinewassendingtraffictoan|P Ididnotrecognize.Itturnsoutt
hat my machine was sending data to a Google IP address of 172.217.11.142. Since I did
not have any Google products running, nor Gmail open, I did not know why this was
happening. I examined my system and found this:
~I$ps-ef
[-I$ps: et 00:00:00/opt/google/chrome/chrome--
It seems that even when Chrome is not running in the foreground it remains running as
service. I would not have necessarily noticed this without a packet analysis to tip me off.
re-captured some more tep dump data but this time told tep dump to write the data to a file
that I opened in Wireshark (more on that later), Here’s that entry:
‘Tep dump is a favorite tool among sysadmins because itis a command-line tool. This means
that it doesn’t require a full-blown desktop to run. It is unusual for production servers to
provide a desktop because of the resources that would take, so command-line tools are
94