1) If a packet is to be delivered to exactly one host in a network, what kind of address should be used to specify the destination?
a. Unicast address
b. Broadcast address
c. Anycast address
d. None of these
Solution: Unicast address is used if a packet is to be delivered to a specific host. Broadcast address is used if a packet has to be delivered to all the hosts within a network or subnetwork. Anycast address is used if a packet has to be delivered to exactly one of the hosts in a network or subnetwork. Hence, the correct option is (c).
2) What is the purpose of HELLO packets in the OSPF protocol?
a. Keep the links between neighbor routers alive.
b. Update routing table by exchanging information between neighbors.
c. For broadcasting link state advertisement information.
d. All of these.
Solution: A HELLO packet received from a neighboring router indicates that the corresponding communication link is up and running. In the OSPF protocol, if the HELLO packet is not received for 40 seconds, it indicates failure of the neighbor or the communication link. Hence the correct option is (a).
3) When an entire IPv6 packet is included as payload inside an IPv4 packet, it is called
d. None of these.
Solution: When entire IPv6 packets are encapsulated within IPv4 packets, it is called tunneling. The IPv6 packet gets transmitted as data over an IPv4 network. Hence, the correct option is (b).
4) Consider the following routing table in a router. On which interface will an IP packet with destination address 220.127.116.11 be forwarded?
Destination Subnet Mask Interface
18.104.22.168 255.255.0.0 Eth0
22.214.171.124 255.255.224.0 Eth1
126.96.36.199 255.255.255.0 Eth2
188.8.131.52 255.255.255.224 Eth3
default 0.0.0.0 Eth2
Row 1: 184.108.40.206 AND 255.255.0.0 = 220.127.116.11 Matches with destination address
Row 2: 18.104.22.168 AND 255.255.224.0 = 22.214.171.124 Matches with destination address
Row 3: 126.96.36.199 AND 255.255.255.0 = 188.8.131.52 No match
Row 4: 184.108.40.206 AND 255.255.255.224 = 220.127.116.11 No match
Row 2 provides the longest prefix match; hence the packet will be forwarded to Eth1.
5) An entry in the routing table has 18.104.22.168 as the destination and /22 as the subnet mask. What will be the network address?
d. None of these.
Solution: In binary notation, 22.214.171.124 = 10000111 00101110 00111000 00000000
If we use /22 as the subnet mask, this means that the first 22 bits of the address must be used to get the network address. If we do this, we get 10000111 00101110 00111000 00000000 = 126.96.36.199 Hence, correct option is (a).