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OSPF - PowerPoint PPT Presentation


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OSPF. Kevin Piper, David Perry, Tom Hoffman, Emely Pagan. Agenda. OSPF overview Configuring single area OSPF lab Router designation Configuring multi-area OSPF lab Verifying and managing OSPF Questions or comments. Overview. OSPF (open shortest path first).

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Presentation Transcript
slide1

OSPF

Kevin Piper, David Perry, Tom Hoffman, Emely Pagan

Valencia Community College

Cisco Networking

agenda
Agenda
  • OSPF overview
  • Configuring single area OSPF lab
  • Router designation
  • Configuring multi-area OSPF lab
  • Verifying and managing OSPF
  • Questions or comments

Valencia Community College

Cisco Networking

overview
Overview
  • OSPF (open shortest path first).
    • A link state protocol. Link state protocols use the shortest path first algorithm to populate the routing table. OSPF shares information with every router on the network.
  • OSPF and Cisco.
    • OSPF is nonproprietary to Cisco.
    • Developed 1988 by internet engineering task force (IETF).
    • Developed to be a interior gateway protocol.
    • Used by routers in the same autonomous system.

Valencia Community College

Cisco Networking

ospf terms
OSPF Terms

Valencia Community College

Cisco Networking

slide5

Configuring Cost

Cost 64.7

Cost 64.7

1.544MB

R4

1.544MB

R3

R5

Cost 1

Cost =1562

Cost =195.1

100MB

56KB

Cost 1562

R1

1.544MB

R2

Cost 64.7

Cost = 10^8 / bandwidth

Valencia Community College

Cisco Networking

pros and cons
Advantages

Supports VLSM

Faster convergence

Efficient bandwidth utilization

No hop-count limit

Path selection based on cost

Loop-free routing environment

Disadvantages

Difficult to configure

More time to plan

CPU/memory intensive

Pros and Cons

Valencia Community College

Cisco Networking

considerations
Considerations
  • Size of the area
  • Number of neighbors per router
  • Problem isolation
  • Restriction of routing information
  • Stable backbone design
  • Addressing areas

Valencia Community College

Cisco Networking

slide8

Length

1 byte

1 byte

2 bytes

4 bytes

4 bytes

2 bytes

2 bytes

8bytes

Version Number

Authentication type

Packet Length

Router ID

Description

Type

Area ID

Check sum

Authentication

24 bytes

4 bytes

2 bytes

1 byte

1 byte

4 bytes

4 bytes

4 bytes

4 bytes each

Length

OSPF Packet Header

Backup designated router

Hello interval

option

Router Priority

Dead interval

Designated router

Additional Neighbor

Description

Netmask

OSPF packet header

Hello Packet

Valencia Community College

Cisco Networking

forming adjacencies
Forming Adjacencies
  • Init state
  • Establish bi-directional communication
  • Exstart
  • Exchange state
  • Loading state
  • Full state

Valencia Community College

Cisco Networking

router adjacencies without designated routers
Router Adjacencies Without Designated Routers

R1

R2

R6

R3

R5

R4

15 Router adjacencies

Valencia Community College

Cisco Networking

router designation
Router Designation
  • Election process
    • Hello Packet
    • Priority
  • Designated router (DR)
  • Backup DR (BDR)
  • DR other

Valencia Community College

Cisco Networking

router adjacencies with designated routers
Router Adjacencies With Designated Routers

R1

R2

R6

R3

R5

BDR

9 Router adjacencies

R4

DR

Valencia Community College

Cisco Networking

configuring single area ospf
Configuring Single Area OSPF

Valencia Community College

Cisco Networking

single area ospf layout
Single Area OSPF Layout

Area 1

131.108.1.2/24

131.108.1.1/24

R3’s Loopback

R3’s Loopback

Router 1

E0

Loopback0 11.11.11.11

E0

Loopback0 22.22.22.22

Switch

Router 2

E0

131.108.1.3/24

Router 3

R3’s Loopback

Loopback0 33.33.33.33

Valencia Community College

Cisco Networking

slide15

Configuration Files

Router 1

Router 2

Router 3

Valencia Community College

Cisco Networking

configuring multi area ospf
Configuring Multi-area OSPF
  • Why use multi-area OSPF ?
  • Advantages
    • Smaller routing tables
    • Less routing update overhead
    • Faster synchronization
  • Disadvantages
    • Complex to implement

Valencia Community College

Cisco Networking

ospf router types
OSPF Router Types
  • Internal
  • Area border router (ABR)
  • Autonomous systems border router (ASBR)
  • Backbone router

Valencia Community College

Cisco Networking

multi area ospf layout
Multi-area OSPF Layout

Switch

131.108.1.2/24

131.108.1.1/24

Area 1

E0

Router 1

E0

Router 2

S0

Area 2

141.108.10.0/30

S1

141.108.10.4/38

Router 3

S1

S0

E0

E0

131.108.26.1/24

131.108.33.1/24

Router 4

Area 0

Valencia Community College

Cisco Networking

slide19

Router 1 configuration

Valencia Community College

Cisco Networking

slide20

Router 2 configuration

Valencia Community College

Cisco Networking

slide21

Router 3 Configuration

Valencia Community College

Cisco Networking

slide22

Router 4 configuration

Valencia Community College

Cisco Networking

verifying and managing ospf
Verifying and Managing OSPF
  • OSPF process
  • OSPF neighbors
  • Interface configuration
  • Link states
  • Timers
  • Debugging

Valencia Community College

Cisco Networking

issues
Issues
  • Redistributing ANYTHING into OSPF

Redistributing OSPF 1

Valencia Community College

Cisco Networking

issues25
Issues
  • Lab closing on 14:00 on Friday.
  • No lab hours on weekends.

Valencia Community College

Cisco Networking