Table of Contents

1 Computer Networks Gate Questions for Practice

Computer Networks Gate Questions for Practice

Objective of this computer network gate questions tutorial is provide computer networks gate questions with answer for the students who are preparing for GATE CS/IT Exam.

In this tutorial we have discussed Computer Networks GATE Exam questions along with some practice questions. Such types of questions are generally asked in GATE CS/IT Exam every year.

Students are suggested to practice these questions.

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Table of Content

After reading this tutorial students will be able to understand the following –

Important Computer Networks Topics for GATE Exam.
Computer Networks GATE Previous Year Solved Questions.
Points to remember in IP Addressing.

Let’s start with computer networks important topics for GATE and UGC NET Exam.

Computer Networks Important Topics for GATE Exam

Some important topics of Computer Networks for GATE CSE Exam are as follows-

IP Addressing and Sub netting.
Sliding Window Protocol.
Hamming Distance and Cycle Redundancy Check
Conceptual knowledge of application layer protocols such as FTP, HTTP, SMTP, POP, DNS, TELNET.
Routing algorithms concepts and routing table.
Ethernet
TCP/IPV4
Encryption and Decryption ( RSA Algorithm Based problem)

Students can find the Computer networks syllabus for GATE CS/IT Exam.

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Computer Networks GATE Exam Questions

In this section we have explained the Previous Year Computer Networks GATE Exam questions in Two Parts. First we explained the Computer Networks questions Consist of 1 Marks after that Questions consisting of 2 marks are explained.

1 Marks Questions

Questions asked in one marks are as follow –

Q1.Which protocol uses UDP as transport protocol?

(a)SMTP

(b)telnet

(c)DNS

(d)HTTP

Answer : c

Explanation

The correct answer is option (c ) DNS on most of the other sources. When I searched it in more detail. Then we have found that

(a ) SMTP can use both UDP and TCP also.

(b) DNS also use both TCP and UDP.

So option a and c both may be correct. But Since SMTP prefer TCP over UDP. So option a may be discarded. Then option C will be the answer.

Q2.Which of the following is false with regards to TTL

(a) TTL is used to avoid infinite looping

(b) TTL is used in debugging

( c ) TTL counts number of routers between source and destination

(d ) TTL used in likening

Answer : d

Explanation

(1) First option is right TTL is used to avoid infinite loop. Distance vector routing protocols use the TTL value in the IP datagram header to avoid Routing Loops.

(2) Second option is also correct. USB to TTL serial code provides an easier way to communicate and helps in debugging the equipment.

(3) Third option is also correct because TTL also count the HOP.

(4) TTL does not use linking.

Q(3): What is protocol data unit at Application Layer in internet stack ?( GATE 2012)

(a) Segment

(b) Datagram

(d) Frame

Answer : C

Explanation

Protocol data unit for different layers are as follow

(i) Application Layer – Message

(ii) Transport Layer – Segment

(iii) Network Layer – Datagram

(iv) Data Link Layer – Frame

Q 4. What is name of Transport Layer Protocol which is used to support the electronic mail ? ( GATE 2012)

(a) SMTP

(b) IP

(d) UDP

Answer : C,

Explanation

Email uses SMTP protocol to send email but SMTP is an application layer protocol and in background this SMTP uses TCP as transport layer protocol to support email. So correct answer is TCP.

Q 5. How many networks can be allowed in Class C under IPV4 ? ( GATE 2012)

(a) 2^14

(b) 2^17

(d) 2^24

Answer : C

Explanation

Since we know that under IPV4 IP addressing in Class C 32 Bits IP address consist two parts host id and network id, 8 bits are used for host id part and 24 bits are used for network id part.

Now among these 24 bits 3 bits are fixed as 110 sp remaining 21 bits are used to form networks and total possible networks are 2^21.

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Q6. If a Firewall which supports 4 layer design can not ( GATE 2011)

(a) Block All ICMP traffic

(b) Block HTTP traffic during 9:00 P.M to 5 A.M

(d) None

Answer : B

Explanation

Since HTTP is a transport layer protocol. Which 5th layer of TCP/IP model.

Q.7 Here some activities related to email is given . Find the correct match for the protocol used in appropriate activity. ( GATE 2011)

A1: send an email from a mail client to mail server.

A2:download an email in mailbox from mail server to mail client

A3: checking mail in browser

(a) A1: HTTP, A2:SMTP, A3: POP

(b) A1:SMTP, A2: FTP , A3:HTTP

(d) A1:POP, A2:SMTP, IA3:ICMP

Answer: C,

Explanation

SMTP is used by user client to den mail, POP is used to download in mailbox from mail sever and checking mail using browser simply uses HTTP.

Q8. IP Header has a field TTL ( Time To Live). Which among the following statement best explain the use of TTL ( GATE 2010)

(a) It can be used to prioritize the packets

(b) It can be used to reduce the delay.

(d) It can be used to prevent packet looping.

Answer: D

Explanation

TTL represent the maximum time limit a data packet can exist in the network. Objective of TTL is to avoid a situation in which an undeliverable datagram keeps circulating.

Q9. An organization has a Class B Network and need to from subnet for 64 departments.

what would be the appropriate Subnet Mask ( GATE 2005)

(a)255.255.0.0

(b)255.255.64.0

(d)255.255.252.0

Answer: d,

Explanation

Since Organization has a class B networks, in class B 16 bits are used for host id and 16 bits are used for network id. Since organization want to form 64 department. SO 6 bits are used to identify the 64 departments so subnet mask will be

11111111.11111111.11111100.00000000 which is 255.255.252.0.

Q10. The address resolution protocol is used for

(a) Finding IP address corresponding to MAC Address

(b)Finding MAC Address corresponds to IP address

(d) Find IP address from DNS

Answer : B

Explanation

If IP address is known and we have to find corresponding Physical address or MAC address the ARP address resolution protocol is used.

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2 Marks Questions

Computer Networking Questions asked in 2 marks are given below –

Q1.Match the following

I.Application Layer a. L2TP

II.Session Layer b. DHCP

III.Physical Layer c. PPP

IV.Data Link Layer d.IEEE 802.3

(p) I – b, ii – a, iii – d,iv-c

(q) i- b, ii-c,iii-d, iv-a

(r) i- c, ii-a, iii-b,iv-d

(s) i- d, ii-c, iii-b, iv-a

Answer – p

Q2.Determine the correct option for the given assertion and reason

Assertion :In IEEE 802.3 is not suitable for client server application

Reason :In Ethernet there is a restriction on minimum size.

(a)Assertion and reason are true but this is not correct reason for the given assertion.

(b)Assertion and reason are false

(c)Assertion and Reason both are true.

(d)Assertion is true and reason is false.

Answer is b

Q3.Consider a class A, Class B and Class C network. Consider the given IP address and subnet mask

IP Address : 150.157.100.70

Subnet Mask : 255.255.224.0

What is the address of the network in which host belong to.

(a)150.157.96.70

(b)150.157.96.0

(d)None

Answer is b

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Q4.A router receives an IP packet containing a data of 300 byte and it is forwarded to a network with maximum transmission unit of 80 bytes. Assume that IP header is 10 Byte long. Find the total fragment , more fragment and offset values

(a) 4, 1110,(0,10,20,30)

(b) 1,1110,(0,8.75,17.5,26.25,35)

(d) none

Answer b

Q5.Match the following

P. This is network address a. Host Id =0

Q. Host is this network b. Inter process communication

R. Loop back address c. All Zero

S. DHCP Client d. Network Id =0

(a) P-a, Q-b, R-c,S-d

(b) P-c, Q-b,R-c,S-d

(d) None

Q6.Find the false statement about HTTP

(a) HTTP run over TCP

(b) HTTP allows information to be stored in url

( c) HTTP describe the structure of web page

( d ) HTTP can be used to test the validity of hyper link test.

Answer – b

Q7. The check sum in IP header must be recomputed at every router because of change in

(a) TTL, header length, fragment offset, TOS , ME

(b) TTL, options, data, fragment offset, MF

( c ) TTL, options, identification, datagram length, fragment offset, MF

( d ) None of the above.

Answer – c

Q8. Which of the following statement is false about message diagram

(a) A change to input 1 bit produce a different output.

(b) Given P, it is easy to compute MD(P).

( c ) Given MD ( P) , it is effectively impossible to find P

( d) Given P we can Find P’ such that MD(p’) =MD(P)

Answer -d

Points to Remember in IP Addressing

Some key points to be remember in IP Addressing for GATE Exam are as shown in following picture. Candidate are kindly requested to remember these points while preparing for GATE Exam.