OSPF Routing

Question 1

What class of protocol is OSPF

Answer 1

OSPF is a classless, link-state routing protocol

Question 2

What is Classless Routing

Answer 2

• Classless routing causes a router to use its default routes for any packet that does not match some other route

Question 3

OSPF Packet Types

Answer 3

• Hello: Used to establish and maintain
  adjacency.
• DBD (Database Description):
  Abbreviated list of the sending router’s
  linkstate database.
• LSR (Link-State Request) : Used by
  routers to request more information
  about any entry in the DBD.
• LSU (Link-State Update): Link-state
  information.
• LSAck (LSA Acknowledgment): Router
  sends a link-state (LSAck) to confirm

Question 4

MCQ - Hello Packet & Neighbour establishment

Answer 4

• Hello Packets are sent by OSPF enabled
  routers to discover their neighbours and
  establish adjacencies.
• Only when the 3 parameters (Hello
  interval, Dead interval and Network Type)
  are agreed, the routers can become
  neighbours

Question 5

Hello and Dead interval

Answer 5

*Hello interval: this defines how often we send the hello
packet.
*Dead interval: this defines how long we should wait for
hello packets before we declare the neighbor dead.

On Ethernet interfaces you will see a 10 second hello
interval and a 40 second dead interval.

Question 6

Enabling OSPFv2 Routing statement

Answer 6

R1(config)# router ospf [ process-id ]
* This command enables OSPF on the router using process-id of 10 in this example

Question 7

Router ID and Network statement

Answer 7

R1(config)#router ospf 10
R1(config-router)#router-id 1.1.1.1
R1(config-router)#network 172.16.3.0 255.255.255.252 area 0
Area 0 is the backbone area

Question 8

OSPF Passive Interface statement

Answer 8

R1(config-router)# passive-interface g0/0

Question 9

Verifying OSPFv2 operation statement (see image in disc)

Answer 9

show ip ospf neighbors

#show ip route (see if route is learning remote routes)

Question 10

What is Link-State

Answer 10

• Link-State - each node independently calculates the next best logical path

Question 11

What is OSPF

Answer 11

It is an open standard and inter-operate across multi vendor environments

Question 12

What is OSPF known for

Answer 12

• It is known for it’s scalability