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n n ro uc on oProtocol

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ome as c oncep s o

Protoco l

Router IDA 32bit signless round number is the onlyidentification of a router, and this is unique

in the entire autonomous system.

Number of the ProtocolThe number of OSPF Protocol is 89.

IP Header(Protocol # 89)

PSPF Packet

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The Topological Structure of the Network

Described by OSPF through the Link Status

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rocess o ou e a cu a ngby OSPF

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e g or a eMachine

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acency e a on e - pProcess between Two Routers

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DR(Designated Router)

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NBMA and Point-to-Multipoint

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OSPF Area Division

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Interarea Route Calculation

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ac one reas an r uaConnection

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x erna ommun ca onwith the Autonomous System

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STUB Areas and Route Convergence

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LSA Classification

Router-LSA is created by each router. It describes the link status and overhead of the router andtransfers themto the whole area.

Network-LSA is created by DR. It describes the link status of the local stub network and transfers it

to the whole area.

Net-Summary-LSA is created by ABR. It describes the routes of a certain stub network inside thearea and transfers themto the related area.

Asbr-Summary-LSA is created by ABR. It describes the routes to ASBR and transfers them to the

related area.

AS-External-LSA is created by ASBR. It describes the routes to the outside of AS and transfers them

to the whole AS (except the STUB area).

n er ace ass ca on an

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n er ace ass ca on an

Router Classfication

A ccord ing t o d i f fe r en t l ink l aye r m e d ia , t he O S P F

p ro toco l i s d iv ided i n to t he fo l l owing 4 t ypes o f

n e t w o r k s : B r o a d c a s t , N B M A , P o in t - t o -P o in t a n d

P o i n t - t o - M u l t i p o i n t

A ccord ing t o t he d i f f e r en t ro l e s p l ayed in t he

a u t o n o m o u s s y s t e m , r o u t e r s c a n b e d i v i d e d i n t o :

IA R , A B R , B B R a n d A S B R A ccord ing t o t he d i f f e r en t t ypes , t he s t a tu s o f an

i n t e r f a c e t h a t r u n s t h e O S P F p r o t o c o l c a n b e d i v i d e d

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Why OSPF Is Loop-Free?

Each LSA (Link Status Broadcast) has marked out

the creator (marked with the Router ID of the router

that creates the LSA). The rest routers only take

charge of transmission. In such a way, there will be

no change or misunderstanding to the messages in t

course of transmission.

The route algorithm is SPF. The calculation result is

tree and the routes are the leaf nodes. From the root

en o un e

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en o un e

Protocol

S c a l e o f n e t w o r k There are more than 10 routers in the network; Middle- or large-scale network.

T o p o lo g y s t r u c t u r e o f n e t w o r k

The topology structure of network is the form of a mesh and each two random routers have the deman

for connection.O t h er sp e ci a l d e m a n d s

It requires the routes to be able to converge very quickly when in change and the overhead of the own

network of the route protocol to be as low as possible.

D e m a n d s o n t h e r o u t e r i t s e l f

In running the OSPF protocol, there are certain demands on the processing capability of the CPU of therouter and on the size of memory. The routers with a poor performance is not recommended to run the

OSPF protocol.

on gure e

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on gure e

Protocol-Divide the Area

Basic principles for area division

Divide according to geographical areas oradministrative regions

Divide according to the high end routers of thenetwork

Divide according to the law of IP address

Some restrictive conditions

Scale of the area

Connectivity to the backbone area

ABR processing capability

e as c on gura on or

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e as c on gura on or

Starting the OSPF Protocol

Configure the Router ID of the router

Quidway(config)#router id A.B.C.D

Start the OSPF ProtocolQuidway(config)#router ospf

Configure the OSPF Area

Quidway(config-router)#networkaddresswildcard-maskarea area-id

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Convergence and Virtual

Links

un e n e

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un e n e

Network

sp ay e unn ng a us

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sp ay e unn ng a us

of OSPF

show ip ospf

show ip ospf error

show ip ospf interface

show ip ospf neighbor

sp ay e e ugg ng

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sp ay e e ugg ngInformation of the OSPF

debug ip ospf event

debug ip ospf lsadebug ip ospf packet

debup ip ospf spf

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OSPF Trouble Shooting

Configuration troubleshootingFirst check whether the OSPF Protocol has been started and configured properly

Local area troubleshooting

Check whether the protocol between two

directly connected routers runs properly.

Global area troubleshootingConsider from the aspect of the network topology structure and check whether the

area is properly configuredOther hard questions

To act according to the practical situations.

If the OSPF does not run properly, checkaccording to the

following steps:

au s e ween e

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au s e ween eNeighboring Routers

E i A Di i i

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Errors in Area Division

Oth P ibl F lt

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Other Possible Faults