Network Layer

Question 71

If there are five routers and six networks in intranet using link state routing, how many routing tables are there?

• 1
• 5
• 6
• 11

Question 72

When a host on network A sends a message to a host on network B, which address does the router look at?

• Port
• IP
• Physical
• Subnet mask

Question 73

Dijkstra’s algorithm is used to

• Create LSAs

• Flood an internet with information

• Calculate the routing tables

• Create a link state database

Question 74

For n devices in a network, ________ number of duplex-mode links are required for a mesh topology.

• n(n + 1)
• n (n – 1)
• n(n + 1)/2
• n(n – 1)/2

Question 75

__________ is a bit-oriented protocol for communication over point-to-point and multipoint links.

• Stop-and-wait
• HDLC
• Sliding window
• Go-back-N

Question 76

In Challenge-Response authentication the claimant ________.

• Proves that she knows the secret without revealing it
• Proves that she doesn’t know the secret
• Reveals the secret
• Gives a challenge

Question 77

Consider two hosts P and Q connected through a router R. The maximum transfer unit (MTU) value of the link between P and R is 1500 bytes, and between R and Q is 820 bytes. A TCP segment of size 1400 bytes was transferred from P to Q through R, with IP identification value as 0×1234. Assume that the IP header size is 20 bytes. Further, the packet is allowed to be fragmented, i.e., Don’t Fragment (DF) flag in the IP header is not set by P. Which of the following statements is/are correct?

• Two fragments are created at R and the IP datagram size carrying the second fragment is 620 bytes.
• If the second fragment is lost, R will resend the fragment with the IP identification value 0×1234.
• If the second fragment is lost, P is required to resend the whole TCP segment.
• TCP destination port can be determined by analysing only the second fragment.

Question 78

Consider a computer network using the distance vector routing algorithm in its network layer. The partial topology of the network is shown below. The objective is to find the shortest-cost path from the router R to routers P and Q. Assume that R does not initially know the shortest routes to P and Q. Assume that R has three neighbouring routers denoted as X, Y and Z. During one iteration, R measures its distance to its neighbours X, Y, and Z as 3, 2 and 5, respectively. Router R gets routing vectors from its neighbours that indicate that the distance to router P from routers X, Y and Z are 7, 6 and 5, respectively. The routing vector also indicates that the distance to router Q from routers X, Y and Z are 4, 6 and 8 respectively. Which of the following statement(s) is/are correct with respect to the new routing table o R, after updation during this iteration?

• The distance from R to P will be stored as 10
• The distance from R to Q will be stored as 7
• The next hop router for a packet from R to P is Y
• The next hop router for a packet from R to Q is Z

Question 79

Host X has IP address 192.168.1.97 and is connected through two routers R1 and R2 to an­other host Y with IP address 192.168.1.80. Router R1 has IP addresses 192.168.1.135 and 192.168.1.110. R2 has IP addresses 192.168.1.67 and 192.168.1.155. The netmask used in the network is 255.255.255.224. 


Given the information above, how many distinct subnets are guaranteed to already exist in the network?

• 6
  

• 3
  

• 2
  

• 1
  

Question 80

Assume that Source S and Destination D are connected through an intermediate router R. How many times a packet has to visit the network layer and data link layer during a transmission from S to D?

• Network layer – 4 times, Data link layer – 4 times
• Network layer – 4 times, Data link layer – 6 times
• Network layer – 2 times, Data link layer – 4 times
• Network layer – 3 times, Data link layer – 4 times