The Gateway to Computer Science Excellence
First time here? Checkout the FAQ!
x
+3 votes
2.5k 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
asked in Computer Networks by (117 points) | 2.5k views

2 Answers

+8 votes

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

answered by Veteran (50.7k points)
0
Sir how did you get  7 entries  ?  can you draw a pic ? thanks
0
Yes please explain about 7 entries ?
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 

Image may contain: text

0
why would it contain 10 entries for routers in its own region,will it contain an entry for its own router.I think 9 should be enough,why would a router address a packet to itself. according to that answer must be 9+8+7=24.correct me if i am wrong..
0 votes
Answer could be like this:

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.
answered by Active (1.1k points)

Related questions

Quick search syntax
tags tag:apple
author user:martin
title title:apple
content content:apple
exclude -tag:apple
force match +apple
views views:100
score score:10
answers answers:2
is accepted isaccepted:true
is closed isclosed:true
50,122 questions
53,241 answers
184,705 comments
70,480 users