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

222 © 2003, Cisco Systems, Inc. All rights reserved. VLSM Labs

333 © 2003, Cisco Systems, Inc. All rights reserved. The largest subnet requires 400 hosts = 2 9 – 2 = 510 possible hosts x.xxxxxxxx =.24.0/23 The next largest subnet requires 200 hosts = 2 8 – 2 = 254 possible hosts xxxxxxxx =.26.0 /24

444 © 2003, Cisco Systems, Inc. All rights reserved. The next largest subnet requires 50 hosts = 2 6 – 2 = 62 possible hosts xxxxxx =.27.0/ 26 The next largest subnet requires 50 hosts = 2 6 – 2 = 62 possible hosts xxxxxx =.27.64/ 26

555 © 2003, Cisco Systems, Inc. All rights reserved. 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

666 © 2003, Cisco Systems, Inc. All rights reserved. Using CIDR the ISP is able to use four consecutive IP address / / / /24 This block can be summarised as / 22

777 © 2003, Cisco Systems, Inc. All rights reserved. In Binary / / / /22 This allows bits borrowed from the network portion to be given to host addresses

8 © 2003, Cisco Systems, Inc. All rights reserved. CCNA 3 v3.0 Module 2 Single-Area OSPF

999 © 2003, Cisco Systems, Inc. All rights reserved. Objectives Link-state routing protocol Single-area OSPF concepts Single-area OSPF configuration

10 © 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

11 © 2003, Cisco Systems, Inc. All rights reserved. Overview of Link-State and Distance Vector Routing

12 © 2003, Cisco Systems, Inc. All rights reserved. How Routing Information Is Maintained

13 © 2003, Cisco Systems, Inc. All rights reserved. Link-State Routing Features P4 knows about its neighbors, P1 and P3, on Perth3 network

14 © 2003, Cisco Systems, Inc. All rights reserved. Link-State Routing Protocol Algorithms

15 © 2003, Cisco Systems, Inc. All rights reserved. Advantages and Disadvantages of Link- State Routing

16 © 2003, Cisco Systems, Inc. All rights reserved. Comparing Distance Vector and Link-State Routing

17 © 2003, Cisco Systems, Inc. All rights reserved. OSPF Overview OSPF is becoming the preferred IGP protocol when compared with RIPv1 and RIPv2 because it is scalable.

18 © 2003, Cisco Systems, Inc. All rights reserved. OSPF Terminology

19 © 2003, Cisco Systems, Inc. All rights reserved. More OSPF Terminology Cost = 100,000,000 / Bandwidth

20 © 2003, Cisco Systems, Inc. All rights reserved. OSPF Databases

21 © 2003, Cisco Systems, Inc. All rights reserved. Comparing OSPF Link State with Distance Vector Routing Protocols

22 © 2003, Cisco Systems, Inc. All rights reserved. Shortest Path Algorithm The best path is the lowest-cost path. Router B has calculated the best path to D

23 © 2003, Cisco Systems, Inc. All rights reserved. OSPF Network Types

24 © 2003, Cisco Systems, Inc. All rights reserved. OSPF Hello Protocol

25 © 2003, Cisco Systems, Inc. All rights reserved. Steps in the Operation of OSPF Discover neighbors

26 © 2003, Cisco Systems, Inc. All rights reserved. Steps in the Operation of OSPF Elect DR and BDR on Multi Access Network

27 © 2003, Cisco Systems, Inc. All rights reserved. Steps in the Operation of OSPF Selecting the Best Route

28 © 2003, Cisco Systems, Inc. All rights reserved. Basic OSPF Configuration

29 © 2003, Cisco Systems, Inc. All rights reserved. Basic OSPF Configuration

30 © 2003, Cisco Systems, Inc. All rights reserved. Configuring OSPF Loopback Address and Router Priority

31 © 2003, Cisco Systems, Inc. All rights reserved. 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.

32 © 2003, Cisco Systems, Inc. All rights reserved. Modifying OSPF Cost Metric

33 © 2003, Cisco Systems, Inc. All rights reserved. Configuring OSPF Authentication

34 © 2003, Cisco Systems, Inc. All rights reserved. Configuring OSPF Timers

35 © 2003, Cisco Systems, Inc. All rights reserved. OSPF - Propagating a Default Route

36 © 2003, Cisco Systems, Inc. All rights reserved. Common OSPF Configuration Issues

37 © 2003, Cisco Systems, Inc. All rights reserved. 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

38 © 2003, Cisco Systems, Inc. All rights reserved. The debug and clear Commands for OSPF Verification