Fully Connected Topology

Correct Answer: Mesh

The best solution for designing a highly reliable IT network topology would be a Mesh topology. A fully connected Mesh topology is highly reliable because it has a direct connection between each pair of nodes. In this topology, if any one connection fails or a node goes down, the network can still operate as usual because of the alternative paths available. This provides excellent fault tolerance and can handle high amounts of traffic, making it a great choice for a network that requires high reliability. Other topologies mentioned: Star, Ring, and Bus are not as reliable. In the star topology, if the central node fails, the whole network goes down. In a ring topology, data transmission may be slower as each node in the network has a turn to transmit the data. The bus topology is the least reliable because if the bus (i.e., the main cable) fails, the whole network goes down.

Correct Answer: 10

In a fully connected mesh network, every node is directly connected to every other node. So each node needs to be connected to N-1 other nodes, where N is the total number of nodes. If the current network has 10 nodes, then each node is connected to 10-1=9 other nodes. Now, when a new node is added, it also needs to be connected to all existing nodes, that mean it needs to be connected to the 10 existing nodes. Therefore, the addition of one more node will require 10 additional connections. This clearly represents it's neither 9, 11, nor 12 but 10 additional connections needed.

Correct Answer: Ring

The best topology for this situation would be the 'Ring' topology. In a ring topology, each device (node) is connected to two others, forming a circular network path. This certainly provides a degree of equal pairwise communication; every device has a direct line to its neighbors, and messages can travel around the ring until they reach their destination. This makes it less costly (in terms of cabling) than a full mesh topology, where every device must have a direct line to every other device. Unlike a mesh topology, however, a ring topology does not offer network redundancy - if one connection fails, it can disrupt the whole network. On the other hand, 'Mesh' is wrong because it is the most expensive among all network topologies since every node is connected to every other node. 'Star' cannot be the right answer because, although it's cheaper than mesh, it doesn't provide equal pairwise communication paths as the central hub or switch is a single point of failure. Finally, 'Bus' is incorrect because it offers the least reliability. In a bus topology, a single cable runs through the entire network with terminators at each end. If the bus (the main cable) fails, the entire network goes down.