111 © 2003, cisco systems, inc. all rights reserved. recap vlsm and cidr

111© 2003, Cisco Systems, Inc. All rights reserved.

RECAP

• VLSM and CIDR


VLSM Labs


• 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


• 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


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


• 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


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


CCNA 3 v3.0 Module 2 Single-Area OSPF


Objectives

• Link-state routing protocol

• Single-area OSPF concepts

• Single-area OSPF configuration


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


Overview of Link-State and Distance Vector Routing


How Routing Information Is Maintained


Link-State Routing Features

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


Link-State Routing Protocol Algorithms


Advantages and Disadvantages of Link-State Routing


Comparing Distance Vector and Link-State Routing


OSPF Overview

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


OSPF Terminology


More OSPF Terminology

Cost = 100,000,000 / Bandwidth


OSPF Databases


Comparing OSPF Link State with Distance Vector Routing Protocols


Shortest Path Algorithm

The best path is the lowest-cost path.

Router B has calculated the best path to D


OSPF Network Types


OSPF Hello Protocol


Steps in the Operation of OSPF

Discover neighbors



Elect DR and BDR on Multi Access Network



Selecting the Best Route


Basic OSPF Configuration


Configuring OSPF Loopback Address and Router Priority


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.


Modifying OSPF Cost Metric


Configuring OSPF Authentication


Configuring OSPF Timers


OSPF - Propagating a Default Route


Common OSPF Configuration Issues


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


The debug and clear Commands for OSPF Verification

111 © 2003, cisco systems, inc. all rights reserved. recap vlsm and cidr

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