2.4k views

Consider a subnet with 720 routers. If a three level hierarchy is choosen with 8 clusters, each containing9 regions of 10 routers, then total number of entries in the routing table is_______

1. 25
2. 27
3. 53
4. 72

If there is no hierarchy each router needs 720 routing table entries. if the subnet is divided into 24 regions of 30 routers each router needs 30 local+ 23 remote entries for a total of 53 entries.If a 3 level hierarchy is chosen with 8 clusters each containing 9 regions of 10 routers then each router need 10 entries for local router 8 entries for routing to other regions within its own cluster and 7 entries for distant cluster for a total of 10+8+7 =25 entries

0
Sir how did you get  7 entries  ?  can you draw a pic ? thanks
0
0

Out of 8 clusters  you are in first cluster within first cluster u r in first region so when u come out of it u need entries for 8 regions and then  u need 7 entries for rest clusters diagram could look like as below

We know that

Cluster * Region * Routers = 720

We use the given formula to find minimum size of Routing table:

( Cluster-1 ) + ( Region-1 ) + Routers

Therefore, here also Cluster = 8, Region = 9 & Routers = 10

( 8-1 ) + ( 9-1 ) + 10 = 7 + 8 + 10 = 25.

1
+1 vote
2