Week 9 LSP

Question 1

LSRP?

Answer 1

Link State Routing Protocol

Question 2

What is Link State Routing Protocol?

Answer 2

A distributed DB Algorithm

Question 3

Steps to DB Algorithm?

Answer 3

1. Each router is responsible for meeting its neighbors and learning who they are
2. Each router constructs a LSA which contains a list of the neighbors (links) and costs to them.
3. The LSA is sent to all routers in the AS and each router stores the most recent LSA from all other routers.
4. Each router now computes best routes to all networks based on the LSA information.

Question 4

What is LSA?

Answer 4

Link State Advertisement

Question 5

Distance Vector?

Answer 5

Entire routing table is sent as an update
Periodically sends update at every 30 or 90 seconds. Consumes more bandwidth
Update are broadcast or multicast
Updates are sent to directly connected neighbor only
Routers don’t have end to end visibility of entire network

Question 6

Link State?

Answer 6

Updates are incremental, and entire routing table is not sent as update
Updates are triggered, not periodic. Consumes less bandwith
Updates are multicast
Update are sent to entire network
No routing loops

Question 7

Examples of Distance Vectors?

Answer 7

RIP, IGRP

Question 8

Examples of Link State?

Answer 8

OSPF, IS-IS

Question 9

OSPF?

Answer 9

Open Shortest Path First

Question 10

What kind of protocol is OSPF?

Answer 10

Link State Protocol

Question 11

Link State routing protocols allow routers to?

Answer 11

Share a common view of the entire network

Question 12

Each router sends out a?

Answer 12

LSAs describing its attached links to all routers in an area

Question 13

Each router needs to hold a ?

Answer 13

Topological Database of the entire area

Question 14

What routing algorithm is used by OSPF?

Answer 14

Shortest Path First (SPF)

Also known as Dijkstra

Question 15

Reason to implement OSFP in a hierarchical design?

Answer 15

Decrease routing overhead
Speed up confergence
Confine network instability to single areas of the network

Question 16

Router ID?

Answer 16

An IP address used to identify the router

Question 17

Neighbors?

Answer 17

Two or more router having an interface on a common network

Question 18

Adjacency?

Answer 18

Permits direct exchange of route updates

Question 19

Designed router?

Answer 19

Elected to minimize adjacencies

Question 20

Backup designed router?

Answer 20

Standby for DR

Question 21

Hello Protocol?

Answer 21

Provides dynamic neighbor discovery

Question 22

Neighbor Database?

Answer 22

List of all OSPF routers for which Hello packets have been seen

Question 23

Topological Database?

Answer 23

Information from all of the LSAs received for an area

Question 24

OSPF Area?

Answer 24

Group of networks and routers sharing a common area ID

Question 25

OSPF Operation steps?

Answer 25

1. Neighbor and adjacency initialization. 2. LSA Flooding 3. Short Path First tree calculation

Question 26

How does neighbor and adjacency initialization works?

Answer 26

An OSPF router forms adjacency with the networks | A DR and BDR are elected in OSPF

Question 27

How does LSA flooding work?

Answer 27

Routers will flood their link-state advertisements

Question 28

How does SPF tree calculation work?

Answer 28

Process of selecting the best route to each network

Question 29

Reserved multicast address for OSPF?

Answer 29

224.0.0.5

Question 30

Each recipient must acknowledge that?

Answer 30

The flooded update has been received

Question 31

What is SPF Tree Calculation based on?

Answer 31

Topology database

Question 32

OSPF Metric?

Answer 32

OSPF use a metric referred to as cost | Cost is associated with every outgoing interface included in SPF tree