RIP and IGRP

Cisco Interview Questions, RIP IGRP Frequently asked questions

  1. Explain RIP, its limitations and why it’s known as Distance Vector?

Ans:- RIP is known as Routing Information Protocol with classification of Distance Vector due to its dependency on hops for reaching out to networks. It has two version 1(Classful) and version 2 ( Classless). It has hop limit till 15 hops- beyond this it will advertise route as poisonous route and therefor becomes unreachable.

  1. Whether RIP supports Broadcast or Multicast?

Ans:- RIP ver 1 supports Broadcast while RIP ver 2 support Multicast with reserved group IP 224.0.0.9.

  1. Why RIP causes overhead in network? What are its Timers?

Ans:- Routers configured with RIP exchange all of its routing table information with others in every 30 seconds. So if assuming that there are 200 RIP networks in one router & there are 10 routers , so there would be 10 routers exchanging the information with each other even if its same info. Therefore, it causes overhead. If its RIPv1- then it will broadcast so every other router will hear the info. For RIPv2 its multicast.

  1. What is RIP’s range in terms of hop count?

Ans:-  15 is the max hop count it will support. For 16 it will become poisonous or unreachable.

  1. What is loop avoidance mechanism used in Routing Protocols? Explain Split Horizon and Split Horizon with Poison Reverse

Ans:-  If every router will keep on exchanging same network info repeatedly even if it’s not desirable, then it will cause loop and overhead.   Split Horizon says that information about a network can’t be sent thru the interface from which it had learnt. Split Horizon with Poison Reverse says that Information about a network can be sent thru the same interface from where it had learnt BUT Only when that Information is about a DOWN Network or Poisonous Network (i.e. Hop count 16).  So that every router updates its Routing table.

  1. Explain IGRP and its metric. What is composite metric does it use? How it’s different than of RIP metric

Ans:- IGRP is also a distance vector protocol and depends upon hop count. Its default limit is 100 and max is 255. But, Its metric is 24 bit composite which includes Bandwidth, Delay, Load, Reliability, MTU. Be default it uses Bandwidth and Delay.  IGRP formula is (10000000/Bandwidth in kbps)+ (Sum of Delay in micro second)/10 .    RIP uses only hop count.

  1. What is Hybrid Routing Protocol? Difference between Distance Vector and Hybrid?

Ans:- Distance vector protocol mainly work on Hop count while Link State protocol keeps information about the complete network. It also maintains neighbor table, topology table. RIP , IGRP are only Distance Vector. EIGRP is hybrid i.e. both Distance vector and Link state. OSPF is only Link state routing protocol.

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