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OSPF Routing Protocol Configuration on Juniper Devices

OSPF Routing Protocol

 

OSPF has 3 types version

OSPv1, OSPv2,OSPv3​​ 

Routers running OSPF will usually use the destination IP Addresses 224.0..0.5 and 224.0.0.6 to send hello packets and LSAs onto the network segment

Uses shortest path

 

OSPF Framework​​ 

****Neighbors

​​ Same subnet OSPF enabled routers

 ​​​​ Adjacency​​ formed using​​ ​​ `HELLO` packet

***LSAs

Link state advertisements

Contains reachable subnet information

***LSDB

Link state database​​ 

Used to store subnet information

Important: OSPF​​ has 3 database​​ 1.​​ LSDB , 2.Candidate db , 3,SPF db

 

OSPv2

OSPF support for classless IP addressing

Encrypted authentication allowed between neighbors

OSPv3

Ipv6​​ support

MOSPF disabled

OSPFv3 can still advertise IPv4 subnets

 

 

CALCULATING THE BEST PATH -

Use​​ Dijkstra​​ (SPF)​​ algorithm ​​ for calculating​​ 

OSPF prefer to use the best network path

OSPF uses the SPF algorithm to find ​​ the lowest cost network path

 

 

OSPF Forming Adjacencies

***OSPF Packet types (5 TYPES)​​ 

​​ 1-Hello  ​​ ​​​​ 

2-Database

3-Link state request

4-Link state updates

5-Link state acknowledgement

Important:Ospf Router id are 32 bit addreses​​ 

How to selecet OSPF Router ID ?

Highest IP Address of all active interfaces

Highest Ip address of all Loopback interfaces

Id specified under [router-options]

For change​​ Route ID​​ ​​ has to​​ router reboot​​ 

Ospf​​ -ERRORS

Incorrect subnet mask

Diffirent Timers

Area ID mismatch

Authentication information wrong ​​ -(Password mismatch ,​​ MTU Mismatches)

 

 

 

OSPF Adjaceny Procces

8 ssteps to Adjaceny

-Down

-Init

-Attempt

-2-way​​ 

-Exstart

-exchange

-Loading

-Full

 

BUILDING THE TOPOLOGY OSPF

OSPF has a mechanism whosch can reduce flooded traffic

Ospf ​​ calls the​​ master router​​ the​​ designated router​​ or​​ DR

A backup router DR is also elected, this is known as the​​ Backup Designated router​​ or​​ BRD

For to be​​ Master:

Priority

Router id

 

Important: Highest Router id ​​ becomes the Designated Route (DR)

 ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​​​ *Priorty degree​​ lowest can be​​  ​​​​ DR​​ 

 ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​​​ *Highest ​​ Router Id​​ and​​ ​​ Priority​​ can be​​ BDR.

Important: if ​​ a new router is added with a higher priorty it will become DR OTHER category

 

MAIN LSA PACKET TYPES

Router

Network

Summary

 

 

OSPF AREAS

SUB SYSTEM = AREAS  ​​​​ 

Areas help reduce the size of the OSPF database

*********Ofspf has​​ 6​​ ​​ area type

Backbone area=0 ​​ 

Normal ​​​​ area

Stub​​ area

Totally stubby​​ area

Not so ​​ totally stubby ​​​​ area

 

 

 

 

OSPF ROUTER TYPES

ABR (area border router)

 

ASBRD (Autonomos system border router)

Backbone router

Internal Router

 

 

 

 

OSPF CONFIGURATION​​ 

Example1:​​ Backbone area​​