Computer Networks MCQ Set 1
1. What is internet?
a) a single network
b) a vast collection of different networks
c) interconnection of local area networks
d) none of the mentioned
Answer
Answer: b [Reason:] None.
2. To join the internet, the computer has to be connected to a
a) internet architecture board
b) internet society
c) internet service provider
d) none of the mentioned
Answer
Answer: c [Reason:] None.
3. Internet access by transmitting digital data over the wires of a local telephone network is provided by
a) leased line
b) digital subscriber line
c) digital signal line
d) none of the mentioned
Answer
Answer: b [Reason:] None.
4. ISP exchanges internet traffic between their networks by
a) internet exchange point
b) subscriber end point
c) isp end point
d) none of the mentioned
Answer
Answer: a [Reason:] None.
5. Which one of the following protocol is not used in internet?
a) HTTP
b) DHCP
c) DNS
d) None of the mentioned
Answer
Answer: d [Reason:] None.
6. IPv6 addressed have a size of
a) 32 bits
b) 64 bits
c) 128 bits
d) 265 bits
Answer
Answer: c [Reason:] None.
7. Internet works on
a) packet switching
b) circuit switching
c) both (a) and (b)
d) none of the mentioned
Answer
Answer: a [Reason:] None.
8. Which one of the following is not an application layer protocol used in internet?
a) remote procedure call
b) internet relay chat
c) resource reservation protocol
d) none of the mentioned
Answer
Answer: c [Reason:] None.
9. Which protocol assigns IP address to the client connected in the internet?
a) DHCP
b) IP
c) RPC
d) none of the mentioned
Answer
Answer: a [Reason:] None.
10. Which one of the following is not used in media access control?
a) ethernet
b) digital subscriber line
c) fiber distributed data interface
d) none of the mentioned
Answer
Answer: d [Reason:] None.
Computer Networks MCQ Set 2
1. IPsec is designed to provide the security at the
a) Transport layer
b) Network layer
c) Application layer
d) Session layer
Answer
Answer: b [Reason:] Network layer is used for transferring the data from transport layer to another layers.
2. In tunnel mode IPsec protects the
a) Entire IP packet
b) IP header
c) IP payload
d) None of the mentioned
Answer
Answer: a [Reason:] It is nothing but adding control bits to the packets.
3. A ___________ is an extension of an enterprise’s private intranet across a public Network such as the Internet across a public Network such as the Internet, creating a secure private connection.
a) VNP
b) VPN
c) VSN
d) VSPN
Answer
Answer: b [Reason:] VIRTUAL PACKET NETWORK.
4. Which component is included in IP security?
a) Authentication Header (AH)
b) Encapsulating Security Payload (ESP)
c) Internet key Exchange (IKE)
d) All of the mentioned
Answer
Answer: d [Reason:] AH, ESP, IKE.
5. WPA2 is used for security in
a) Ethernet
b) Bluetooth
c) Wi-Fi
d) None of the mentioned
Answer
Answer: c [Reason:] WPA2 is best with Wi-Fi connection.
6. An attempt to make a computer resource unavailable to its intended users is called
a) Denial-of-service attack
b) Virus attack
c) Worms attack
d) Botnet process
Answer
Answer: a [Reason:] Denial of service attack.
7. Extensible authentication protocol is authentication framework frequently used in
a) Wired personal area network
b) Wireless networks
c) Wired local area network
d) None of the mentioned
Answer
Answer:b [Reason:]Most data transfer is with wireless networks.
8. Pretty good privacy (PGP) is used in
a) Browser security
b) Email security
c) FTP security
d) None of the mentioned
Answer
Answer: b [Reason:] PGP is at email security.
9. PGP encrypts data by using a block cipher called
a) International data encryption algorithm
b) Private data encryption algorithm
c) Internet data encryption algorithm
d) None of the mentioned
Answer
Answer: a [Reason:] PGP encrypts data by using a block cipher called international data encryption algorithm.
10. When a DNS server accepts and uses incorrect information from a host that has no authority giving that information, then it is called
a) DNS lookup
b) DNS hijacking
c) DNS spoofing
d) None of the mentioned
Answer
Answer: c [Reason:] DNS spoofing is the phenomenon for the above mentioned transaction.
Computer Networks MCQ Set 3
1. Which of the following is not applicable for IP?
a) Error reporting
b) Handle addressing conventions
c) Datagram format
d) Packet handling
Answer
Answer: a [Reason:] Error reporting is handled by ICMP.
2. Which of the following field in IPv4 datagram is not related to fragmentation?
a) Flags
b) Offset
c) TOS
d) Identifier
Answer
Answer: c [Reason:] TOS type of service identifies the type of packets.
3. The TTL field has value 10. How many routers (max) can process this datagram?
a) 11
b) 5
c) 10
d) 1
Answer
Answer: c [Reason:] TTL field is decremented by one each time the datagram is processed by a router.
4. If the value in protocol field is 17, the transport layer protocol used is _________
a) TCP
b) UDP
c) Either of the mentioned
d) None of the mentioned
Answer
Answer: b [Reason:] For TCP it is 6.
5. Which field helps to check rearrangement of the fragments?
a) offset
b) flag
c) ttl
d) identifier
Answer
Answer: a [Reason:] Offset field specifies where the fragment fits in the original datagram.
6. The size of IP address in IPv6 is
a) 4bytes
b) 128bits
c) 8bytes
d) 100bits
Answer
Answer: b [Reason:] An IPv6 address is 128 bits long.
7. The header length of an IPv6 datagram is ___________
a) 10bytes
b) 25bytes
c) 30bytes
d) 40bytes
Answer
Answer: d [Reason:] IPv6 datagram has fixed header length of 40bytes, which results is faster processing of the datagram.
8. In the IPv6 header, the traffic class field is similar to which field in the IPv4 header?
a) Fragmentation field
b) Fast switching
c) TOS field
d) Option field
Answer
Answer: c [Reason:] This field enables to have different types of IP datagram.
9. IPv6 does not use ________ type of address
a) Broadcast
b) Multicast
c) Any cast
d) None of the mentioned
Answer
Answer: a [Reason:] Broadcast has been eliminated in IPv6.
10. Which are the features present in IPv4 but not in IPv6?
a) Fragmentation
b) Header checksum
c) Options
d) All of the mentioned
Answer
Answer: d [Reason:] All the features are only present in IPv4 and not IPv6.
Computer Networks MCQ Set 4
1.A network administrator is connecting hosts A and B directly through their Ethernet interfaces, as shown in the illustration. Ping attempts between the hosts are unsuccessful. What can be done to provide connectivity between the hosts?
1. A crossover cable should be used in place of the straight-through cable.
2. A rollover cable should be used in place of the straight-through cable.
3. The subnet masks should be set to 255.255.255.192.
4. A default gateway needs to be set on each host.
5. The subnet masks should be set to 255.255.255.0.
a) 1 only
b) 2 only
c) 3 and 4 only
d) 1 and 5 only
Answer
Answer: d [Reason:] First, if you have two hosts directly connected, as shown in the graphic, then you need a crossover cable. A straight-through cable won’t work. Second, the hosts have different masks, which puts them in different subnets. The easy solution is just to set both masks to 255.255.255.0 (/24).
2. Your router has the following IP address on Ethernet0: 172.16.2.1/23. Which of the following can be valid host IDs on the LAN interface attached to the router?
1. 172.16.1.100
2. 172.16.1.198
3. 172.16.2.255
4. 172.16.3.0
a) 1 only
b) 2 and 3 only
c) 3 and 4 only
d) None of the mentioned
Answer
Answer: c [Reason:] The router’s IP address on the E0 interface is 172.16.2.1/23, which is 255.255.254.0. This makes the third octet a block size of 2. The router’s interface is in the 2.0 subnet, and the broadcast address is 3.255 because the next subnet is 4.0. The valid host range is 2.1 through 3.254. The router is using the first valid host address in the range.
3. Which two statements describe the IP address 10.16.3.65/23?
1. The subnet address is 10.16.3.0 255.255.254.0.
2. The lowest host address in the subnet is 10.16.2.1 255.255.254.0.
3. The last valid host address in the subnet is 10.16.2.254 255.255.254.0.
4. The broadcast address of the subnet is 10.16.3.255 255.255.254.0.
a) 1 and 3
b) 2 and 4
c) 1, 2 and 4
d) 2, 3 and 4
Answer
Answer: b [Reason:] The mask 255.255.254.0 (/23) used with a Class A address means that there are 15 subnet bits and 9 host bits. The block size in the third octet is 2 (256 – 254). So this makes the subnets in the interesting octet 0, 2, 4, 6, etc., all the way to 254. The host 10.16.3.65 is in the 2.0 subnet. The next subnet is 4.0, so the broadcast address for the 2.0 subnet is 3.255. The valid host addresses are 2.1 through 3.254.
4. What is the maximum number of IP addresses that can be assigned to hosts on a local subnet that uses the 255.255.255.224 subnet mask?
a) 14
b) 15
c) 16
d) 30
Answer
Answer: d [Reason:] A /27 (255.255.255.224) is 3 bits on and 5 bits off. This provides 8 subnets, each with 30 hosts. Does it matter if this mask is used with a Class A, B, or C network address? Not at all. The number of host bits would never change.
5. You need to subnet a network that has 5 subnets, each with at least 16 hosts. Wohich classful subnet mask would you use
a) 255.255.255.192
b) 255.255.255.224
c) 255.255.255.240
d) 255.255.255.248
Answer
Answer: b [Reason:] You need 5 subnets, each with at least 16 hosts. The mask 255.255.255.240 provides 16 subnets with 14 hosts-this will not work. The mask 255.255.255.224 provides 8 subnets, each with 30 hosts. This is the best answer.
6. You have a network that needs 29 subnets while maximizing the number of host addresses available on each subnet. How many bits must you borrow from the host field to provide the correct subnet mask?
a) 2
b) 3
c) 4
d) 5
Answer
Answer: d [Reason:] A 240 mask is 4 subnet bits and provides 16 subnets, each with 14 hosts. We need more subnets, so let’s add subnet bits. One more subnet bit would be a 248 mask. This provides 5 subnet bits (32 subnets) with 3 host bits (6 hosts per subnet). This is the best answer.
7. If an Ethernet port on a router were assigned an IP address of 172.16.112.1/25, what would be the valid subnet address of this host?
a) 172.16.112.0
b) 172.16.0.0
c) 172.16.96.0
d) 172.16.255.0
Answer
Answer: a [Reason:] A /25 mask is 255.255.255.128. Used with a Class B network, the third and fourth octets are used for subnetting with a total of 9 subnet bits, 8 bits in the third octet and 1 bit in the fourth octet. Since there is only 1 bit in the fourth octet, the bit is either off or on-which is a value of 0 or 128. The host in the question is in the 0 subnet, which has a broadcast address of 127 since 128 is the next subnet
8. You have an interface on a router with the IP address of 192.168.192.10/29. Including the router interface, how many hosts can have IP addresses on the LAN attached to the router interface?
a) 6
b) 8
c) 30
d) 32
Answer
Answer: a [Reason:] A /29 (255.255.255.248), regardless of the class of address, has only 3 host bits. Six hosts is the maximum number of hosts on this LAN, including the router interface.
9. What is the subnetwork number of a host with an IP address of 172.16.66.0/21?
a) 172.16.36.0
b) 172.16.48.0
c) 172.16.64.0
d) 172.16.0.0
Answer
Answer: c [Reason:] A /21 is 255.255.248.0, which means we have a block size of 8 in the third octet, so we just count by 8 until we reach 66. The subnet in this question is 64.0. The next subnet is 72.0, so the broadcast address of the 64 subnet is 71.255.
10. The network address of 172.16.0.0/19 provides how many subnets and hosts?
a) 7 subnets, 30 hosts each
b) 8 subnets, 8,190 hosts each
c) 8 subnets, 2,046 hosts each
d) 7 subnets, 2,046 hosts each
Answer
Answer: b [Reason:] A CIDR address of /19 is 255.255.224.0. This is a Class B address, so that is only 3 subnet bits, but it provides 13 host bits, or 8 subnets, each with 8,190 hosts.
Computer Networks MCQ Set 5
1. An OSPF router receives an LSA, the router checks its sequence number, and this
number matches the sequence number of the LSA that the receiving router already has.
What does the receiving router do with the LSA?
a) Ignores the LSA
b) Adds it to the database
c) Sends newer LSU update to source router
d) Floods the LSA to the other routers
Answer
Answer: a [Reason:] An OSPF router receives an LSA, the router checks its sequence number, and this number matches the sequence number of the LSA that the receiving router already has Ignores the LSA.
2. An OSPF router receives an LSA. The router checks its sequence number and finds that
this number is higher than the sequence number it already has. Which two tasks does
the router perform with the LSA?
a) Ignores the LSA
b) Adds it to the database
c) Sends newer LSU update to source router
d) Floods the LSA to the other routers
Answer
Answer: b [Reason:] An OSPF router receives an LSA. The router checks its sequence number and finds that this number is higher than the sequence number Adds it to the database, Floods the LSA to the other routers.
3. An OSPF router receives an LSA. The router checks its sequence number and finds that
this number is lower than the sequence number it already has. What does the router do
with the LSA?
a) ignores the LSA
b) adds it to the database
c) sends newer LSU update to source router
d) floods the LSA to the other routers
Answer
Answer: c [Reason:] An OSPF router receives an LSA. The router checks its sequence number and finds that this number is lower than the sequence number sends newer LSU update to source router.
4. Each LSA has its own age timer. By default, how long does an LSA wait before requiring an update?
a) 30 seconds
b) 1 minute
c) 30 minutes
d) 1 hour
Answer
Answer: c [Reason:] Each LSA has its own age timer. By default, 30 minutes does an LSA wait before requiring an update.
5. Distance vector protocols use the concept of split horizon, but link-state routing protocols, such as OSPF, do not.
a) True
b) False
Answer
Answer: b [Reason:] Distance vector protocols use the concept of split horizon, but link-state routing protocols, such as OSPF, do not use this.
6. The outcome of Dijkstra’s calculation is used to populate the __________
a) Topology table
b) Routing table
c) Neighbor table
d) Adjacency table
Answer
Answer: b [Reason:] The outcome of Dijkstra’s calculation is used to populate the Routing table.
7. What is the IP protocol number for OSPF packets?
a) 89
b) 86
c) 20
d) 76
Answer
Answer: a [Reason:] 89 is the IP protocol number for OSPF packets.
8. Which packet is NOT an OSPF packet type?
a) LSU
b) LSR
c) DBD
d) Query
Answer
Answer: d [Reason:] Query packet is NOT an OSPF packet type.
9. Which multicast address does the OSPF Hello protocol use?
a) 224.0.0.5
b) 224.0.0.6
c) 224.0.0.7
d) 224.0.0.8
Answer
Answer: a [Reason:] 224.0.0.5 is the multicast address does the OSPF Hello protocol use.
10. The Hello protocol sends periodic updates to ensure that a neighbor relationship is maintained between adjacent routers.
a) True
b) False
Answer
Answer: a [Reason:] The Hello protocol sends periodic updates to ensure that a neighbor relationship is maintained between adjacent routers.
11. DBD packets are involved during which two states?
a) Exstart
b) Loading
c) Exchange
d) Two-way
Answer
Answer: a [Reason:] DBD packets are involved during which two states Exstart, Exchange.
12. At which interval does OSPF refresh LSAs?
a) 10 seconds
b) 30 seconds
c) 30 minutes
d) 1 hour
Answer
Answer: d [Reason:] None.
13. Which field is NOT a field within an OSPF packet header?
a) Packet length
b) Router ID
c) Authentication type
d) Maxage time
Answer
Answer: d [Reason:] Maxage timeis NOT a field within an OSPF packet header.
14. Which two commands are required for basic OSPF configuration?
a) Network ip-address mask area area-id
b) Network ip-address wildcard-mask area area-id
c) Router ospf process-id
d) IP router ospf
Answer
Answer: b, c [Reason:] Network ip-address wildcard-mask area area-id, Router ospf process-id are required for basic OSPF configuration.
15. Which OSPF show command describes a list of OSPF adjacencies?
a) Show ipospf interface
b) Show ipospf
c) Show ip route
d) Show ipospf neighbor
Answer
Answer: d [Reason:] Show ipospf neighborOSPF show command describes a list of OSPF adjacencies.
