Question 6916 – UGC NET CS 2015 Dec – paper-3

Consider a subnet with 720 routers. If a three-level hierarchy is chosen with eight clusters, each containing 9 regions of 10 routers, then the total number of entries in the routing table is __________.

Correct Answer: A

Question 12 Explanation:

For example, consider a subnet with 720 routers. If there is no hierarchy, each router needs 720 routing table entries.
If the subnet is partitioned into 24 regions of 30 routers each, each router needs 30 local entries plus 23 remote entries for a total of 53 entries.
If a three-level hierarchy is chosen, with eight clusters, each containing 9 regions of 10 routers, each router needs 10 entries for local routers, 8 entries for routing to other regions within its own cluster, and 7 entries for distant clusters, for a total of 25 entries.