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OSPF

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Content

Introduce OSPF

Operation of OSPF

OSPF Network Type OSPF Area Structure

OSPF Multi Area Routing

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Classification of Routing Protocol

Interior Gateway Protocols Exterior Gateway

Protocols

Distance Vector L ink State Path vector

Classful RIP IGRP EGP

Classless RIPv2 EIGRP OSPFv2 IS-IS BGPv4

IPv6 RIPng EIGRP

for IPv6

OSPFv3 IS-IS

forIPv6

BGPv4 for IPv6

Overview

Classification of Routing Protocol

Interior Gateway Protocols Exterior Gateway

Protocols

Distance Vector L ink State Path vector

Classful RIP IGRP EGP

Classless RIPv2 EIGRP OSPFv2 IS-IS BGPv4

IPv6 RIPng EIGRP

for IPv6

OSPFv3 IS-IS

forIPv6

BGPv4 for IPv6

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Router ID

Adjacency

LSATopology Table

SPF AlgorithmSPF

treeRouting table

OSPF Operation

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OSPF Packet

Hello To discover neighbors and form DR/BDR relationship and

exchange neighbor capabilities.

DBD Check for database synchronization between routers

Link-state

request

Requests specific link-state records from another router

Link-state

update

Sends specifically requested link-state records

Link-state

acknowledge

Acknowledges the other packet types

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Neighbors & Adjacencies

Hello

The routers sends & received

hello packets to & from its

neighbor router

After 2 router establishAdjacency, they synchronize

their LSDBs with each other

Ther routers are full adjacency

with each other

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Before two routers can form an OSPF neighbor

adjacency, they must agree on these values:

Hello Interval

Dead Interval

IP MTU must match

Area ID

Stub Area Flag

Authentication Password


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Down State This state means that no information has been received from neighbor yet

Attemp State Use in NBMA environment. Ther router sends unicast hello packets every poll interval to

the neighbor

I ni t State This state specifies that the router has received a hello packet from its neighbor, but the

receiving router's ID was not included in the hello packet.

2-way State This state designates that bi-directional communication has been established between

two routers. Bi-directional means that each router has seen the other's hello packet.

Exstar t State Once the DR and BDR are elected, the actual process of exchanging link state

information can start between the routers and their DR and BDR.

Exchange State OSPF routers exchange database descriptor (DBD) packets. Database descriptors contain

link-state advertisement (LSA) headers only and describe the contents of the entire link-state database.

Loading State The actual exchange of link state information occurs. Based on the information provided

by the DBDs, routers send link-state request packets. The neighbor then provides the

requested link-state information in link-state update packets

Ful l State All the router and network LSAs are exchanged and the routers' databases are fully

synchronized.

Neighbors State

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OSPF uses costas the metric for determining the best

route

Cost=---------------------------

Default Reference Bandwidth = 10

OSPF Metric

Reference Bandwidth

Bandwidth

8

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Interface Type Bandwidth Default cost

9.6 kbps line 9.6 kbps 10,416

56 kbps l ine 56 kbps 1,785

64 kbps l ine 64 kbps 1,562

T1 cir cui t 1.544 Mbps 64E1 cir cuit 2.048 Mbps 48

T3 cir cui t 45 Mbps 2

Ethernet 10 Mbps 10

Fast Ethernet 100 Mbps 1

Gigabit Ethernet 1 Gbps 1

10 Gigabit Ethernet 10 Gbps 1

4 Mbps Token Ring 4 Mbps 25

OSPF Metric

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Shortest Path First Algorithm

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Shortest Path First Algorithm

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Basic OSPF Configuration

192.168.12.0/24 192.168.23.0/24

.1 .2 .2 .3R1 R2 R3

R1(config)#router ospf 1

R1(config-router)#router-id 1.1.1.1

R1(config-router)#network 192.168.12.1 0.0.0.0 area 0





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Point to Point

Broadcast Multi Access

Non Broadcast Multi Access

Point to Multipoint

Point to Multipoint Non Broadcast

OSPF Network Type

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Hello Interval 10 s Dead Interval 40 s

No DR/BDR election

Multicast updates 224.0.0.5

Neighbor automatic

Point to Point

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Hello Interval 30 s

Dead Interval 120 s

DR/BDR election

Updates are sent as unicast

Neighbor manual

Non Broadcast Multi Access

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Cisco proprietary

Host route are added inrouting table

Hello Interval 10 s

Dead Interval 40 s

No DR/BDR election

Multicast updates224.0.0.5

Neighbor automatic

Point to Multipoint

HUB

SPOKE SPOKE

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Cisco proprietary

Host route are added

in routing table

Hello Interval 30 s

Dead Interval 120 s

No DR/BDR election

Unicast Update

Neighbor manual

Point to Multipoint non Broadcast

HUB

SPOKE SPOKE

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Electing DR& BDR

Highest priority

Highest IP Loop back

Interface

Highest IP Physical

Interface

DROther send update

Multicast 224.0.0.6 to DR

& BDR

OSPF & Multi Access Media

DRBDR

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DR send update Multicast

224.0.0.5 to all other

router

OSPF & Multi Access Media

DRBDR

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Configuration OSPF in NBMA

Router(config)#inteface f0/0

Router(config-if)#ip ospf network non-broadcast

Router(config)#router ospf 1

Router(config-router)#neighbor 192.168.0.2



R1

R2

R3

R4

192.168.0.0/24.1

.2

.3

.4

F0/0

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OSPF Area Structure

OSPF Hierarchical

network structure

To reduce SPF

calculations Backbone Area

(Area 0)

None Backbone Area

( Regular Area)

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OSPF Router Type

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OSPF LSA

LSA Type 1

(Router LSA)

Generated by all routers in an area to describe their directly

attached links (Intra-area routes)

LSA Type 2

(Network LSA)

Generated by the DR of a broadcast or Nonbroadcast segment to

describe the neighbors connected to the segment

LSA Type 3(Summary LSA)

Generated by the ABR to describe a route to neighbors outside thearea. (Inter-area routes)

LSA Type 4

(Summary LSA)

Generated by the ABR to describe a route to an ASBR to neighbors

outside the area

LSA Type 5

(External LSA)

Generated by ASBR to describe routes redistributed into the area

LSA Type 6

(Multi cast LSA)

Not support on Cisco Router

LSA Type 7

(NSSA External

LSA)

Generated by an ASBR inside a NSSA to describe routes

redistributed into the NSSA. LSA 7 is translated into LSA 5 as it

leaves the NSSA

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OSPF Standard Area

Type 1/2 Type 1/2

Type 3

Type 5

Type 4

Area 0 Area 10

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OSPF Stub Area

Type 1/2 Type 1/2

Type 3

Area 0 Stub Area 10

Default Route

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OSPF Totally Stuby Area

Type 1/2 Type 1/2

Area 0 Totallly Stuby Area 10

Default Route

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OSPF Not So Stuby Area

Type 1/2 Type 1/2

Type 4

Area 0 Not So Stubby Area 10

Type 7Type 5

Default Route

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OSPF Multi Area RoutingArea 0

Area 1Area 2

Virtual link Or GRE Tunnel

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OSPF Multi Area RoutingArea 0Area 0

Virtual link Or GRE Tunnel

Area 2

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Configuration Virtual Link

Area 0Area 0Area 2

R2 R4

R2



R2(config-router)#area 1 virtual-link 4.4.4.4

R4



R4(config-router)#area 1 virtual-link 2.2.2.2

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Configuration GRE Tunnel

192.168.24.0/24

Area 0Area 0Area 2

R2 R4

R2

R2(config)#interface Tunnel 24

R2(config-if)#ip address 10.0.24.2 255.255.255.0

R2(config-if)#tunnel source FastEthernet 0/1

R2(config-if)#tunnel destination 192.168.24.4

10.0.0.0/24

R4

R4(config)#interface Tunnel 24

R4(config-if)#ip address 10.0.24.4 255.255.255.0

R4(config-if)#tunnel source FastEthernet 0/0

R4(config-if)#tunnel destination 192.168.24.2

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THANK YOU FOR ATTENTION

ospf v2

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