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Semelhante a CCNA Discovery 3 - Chapter 6 (20)
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CCNA Discovery 3 - Chapter 6
- 1. Routing With a
Link-State Protocol
Introducing Routing and Switching in the Enterprise –
Chapter 6
Version 4.0 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 1
- 2. Objectives
Describe and plan a network using OSPF.
Design and configure a network using single-area
OSPF.
Work with multi-protocol environments.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 2
- 3. Describe and Plan a Network Using
OSPF
Link-state routing protocol
Open standard developed by IETF
Classless interior gateway protocol
Divides the network into areas for scalability
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 3
- 4. Describe and Plan a Network Using
OSPF
Bandwidth determines the cost of a link
Higher bandwidth = lower cost = desirable route
• Cost = 100,000,000 / bandwidth of link in bps
• Manual cost configuration at an interface: ip ospf cost
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 4
- 5. Describe and Plan a Network Using OSPF
SPF algorithm (Diijkstra’s Algorithm)
Each router has a topological tree
SPF tree information stored in topology database
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 5
- 6. Describe and Plan a Network Using
OSPF
Adjacencies: neighbor relationships
Hello protocol
Router ID
Role of loopback interfaces
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 6
- 7. Describe and Plan a Network Using OSPF
Designated router (DR)
Backup designated router (BDR)
DROther
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 7
- 8. Describe and Plan a Network Using
OSPF
Area 0
Roles of routers in an OSPF Autonomous System:
Area Border Router (ABR)
Autonomous System Border Router (ASBR)
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 8
- 9. Design and Configure a Network Using
Single-Area OSPF
OSPF configuration steps:
Enable OSPF + process ID
Advertise networks + wildcard mask and area ID
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 9
- 10. Design and Configure a Network Using
Single-Area OSPF
Authentication protects integrity of routing information
Simple password authentication
Message Digest 5 (MD5)
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 10
- 11. Design and Configure a Network Using
Single-Area OSPF
Tune OSPF parameters:
Interface priority
Router ID
Loopback and interface addresses
Bandwidth (cost )
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 11
- 12. Design and Configure a Network Using
Single-Area OSPF
Verification and troubleshooting commands:
show ip ospf neighbor
show ip protocols, show ip route
show ip ospf, show ip ospf interface
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 12
- 13. Work with Multi-Protocol Environments
Default route configured on ASBR
ASBR distributes the route into the OSPF network
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 13
- 14. Work with Multi-Protocol Environments
Benefits of OSPF summarization:
Reduces number of networks advertised
Reduces memory requirements
Reduces number of entries in router updates
Isolates flapping and other problems to their location
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 14
- 15. Work with Multi-Protocol Environments
OSPF limitations:
Increased router memory and processing demands
Strict design requirements
Knowledgable administrator required
Initial discovery process takes up network bandwidth
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 15
- 16. Work with Multi-Protocol Environments
Administrative distance (AD) determines routes that
appear in routing table
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 16
- 17. Summary
OSPF is a classless interior link-state routing protocol
used in enterprise networks
OSPF uses bandwidth to generate the cost metric
OSPF routers elect a DR and BDR on multi-access
networks
Router ID or router priority can be used to dictate the
selection of DR and BDR
The OSPF network command uses a wildcard mask
Default route distribution and inter-area route
summarization are used in OSPF networks
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 17
- 18. © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 18