111 © 2003, Cisco Systems, Inc. All rights reserved. RECAP VLSM and CIDR.

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RECAP

• VLSM and CIDR

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VLSM Labs

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• The largest subnet requires 400 hosts = 29

– 2 = 510 possible hosts

• 192.168.0001100x.xxxxxxxx = .24.0/23

• The next largest subnet requires 200 hosts = 2 8 – 2 = 254 possible hosts

• 192.168.00011010.xxxxxxxx = .26.0 /24

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• The next largest subnet requires 50 hosts = 26 – 2 = 62 possible hosts

• 192.168.00011011.00xxxxxx = .27.0/ 26

• The next largest subnet requires 50 hosts = 26 – 2 = 62 possible hosts

• 192.168.00011011.01xxxxxx = .27.64/ 26

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CIDR / Supernetting Example

• Company A requires 945 IP addresses

• Using the old system it can be assigned either a Class B address or 4 Class C address

• This would generate 4 entries in the ISP routing table

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• Using CIDR the ISP is able to use four consecutive IP address

• 200.10.0.0 / 24

• 200.10.1.0 / 24

• 200.10.2.0 / 24

• 200.10.3.0 /24

• This block can be summarised as 200.10.0.0/ 22

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In Binary

• 200.10.00000000.0 / 22

• 200.10.00000001.0 / 22

• 200.10.00000010.0 / 22

• 200.10.00000011.0 /22

• This allows bits borrowed from the network portion to be given to host addresses

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CCNA 3 v3.0 Module 2 Single-Area OSPF

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Objectives

• Link-state routing protocol

• Single-area OSPF concepts

• Single-area OSPF configuration

101010© 2003, Cisco Systems, Inc. All rights reserved.

Link-state routing protocols perform the following functions:

• Respond quickly to network changes

• Send triggered updates only when a network change has occurred

• Send periodic updates known as link-state refreshes

• Use a hello mechanism to determine the reachability of neighbors

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Overview of Link-State and Distance Vector Routing

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How Routing Information Is Maintained

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Link-State Routing Features

P4 knows about its neighbors, P1 and P3, on Perth3 network

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Link-State Routing Protocol Algorithms

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Advantages and Disadvantages of Link-State Routing

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Comparing Distance Vector and Link-State Routing

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OSPF Overview

OSPF is becoming the preferred IGP protocol when compared with RIPv1 and RIPv2 because it is scalable.

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OSPF Terminology

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More OSPF Terminology

Cost = 100,000,000 / Bandwidth

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OSPF Databases

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Comparing OSPF Link State with Distance Vector Routing Protocols

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Shortest Path Algorithm

The best path is the lowest-cost path.

Router B has calculated the best path to D

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OSPF Network Types

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OSPF Hello Protocol

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Steps in the Operation of OSPF

Discover neighbors

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Steps in the Operation of OSPF

Elect DR and BDR on Multi Access Network

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Steps in the Operation of OSPF

Selecting the Best Route

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Basic OSPF Configuration

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Basic OSPF Configuration

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Configuring OSPF Loopback Address and Router Priority

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Setting OSPF Priority

The priorities can be set to any value from 0 to 255. A value of 0 prevents that router from being elected. A router with the highest OSPF priority will win the election for DR.

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Modifying OSPF Cost Metric

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Configuring OSPF Authentication

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Configuring OSPF Timers

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OSPF - Propagating a Default Route

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Common OSPF Configuration Issues

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Verifying OSPF Configuration

• show ip protocol

• show ip route

• show ip ospf interface

• shop ip ospf

• show ip ospf neighbor detail

• show ip ospf database

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The debug and clear Commands for OSPF Verification