OSPF DESIGN GUIDE

The Open Shortest Path First Protocol (OSPF), defined in RFC 1583, is an Interior Gateway Protocol used to distribute routing information within a single Autonomous System. This paper examines how OSPF works and how it can be used to design and build today's large and complicated networks.

Index

Section 1:

• 1.0 - Introduction
  • 1.1 - OSPF vs. RIP
  • 1.2 - What do we mean by Link-States?
  • 1.3 - Link-State Algorithm
• 2.0 - Shortest Path Algorithm
  • 2.1 - OSPF cost
  • 2.2 - Shortest Path Tree
• 3.0 - Areas and Border Routers
• 4.0 - Link-State Packets
• 5.0 - Enabling OSPF on the router
• 6.0 - OSPF Authentication
  • 6.1 - Simple password authentication
  • 6.2 - Message Digest authentication
• 7.0 - The Backbone and area 0
• 8.0 - Virtual links
  • 8.1 - Areas not physically connected to area 0
  • 8.2 - Partitioning the backbone
• 9.0 - Neighbors
• 10.0 - Adjacencies
  • 10.1 - DR Election
  • 10.2 - Building the Adjacency
  • 10.3 - Adjacencies on point-to-point interfaces
  • 10.4 - Adjacencies on Non-Broadcast Multi-Access (NBMA)

Section 2:

• 11.0 - Avoiding DRs and "neighbor" command on NBMA
  • 11.1 - Point-to-point subinterfaces
  • 11.2 - Selecting Interface Network Types
    • 11.2.1 - Point-to-multipoint interfaces
    • 11.2.2 - Broadcast interfaces
• 12.0 - OSPF and Route Summarization
  • 12.1 - Inter-area route summarization
  • 12.2 - External route summarization
• 13.0 - Stub Areas
• 14.0 - Redistributing routes into OSPF
  • 14.1 - E1 vs. E2 external routes
• 15.0 - Redistributing OSPF into other protocols
  • 15.1 - Use of a valid metric
  • 15.2 - VLSM
  • 15.3 - Mutual Redistribution
• 16.0 - Injecting defaults into OSPF
• 17.0 - OSPF Design Tips
  • 17.1 - Number of routers per area
  • 17.2 - Number of neighbors
  • 17.3 - Number of areas per ABR
  • 17.4 - Full mesh vs. Partial Mesh
  • 17.5 - Memory issues
• 18.0 - Summary

Section 3:

• 19.0 - APPENDIX A: Link-State Database Synchronization
• • 19.1 - Link-State Advertisements
  • 19.2 - OSPF database example
    • 19.2.1 - General view of the data base
    • 19.2.2 - Router Links
    • 19.2.3 - Network Links
    • 19.2.4 - Summary Links
    • 19.2.5 - Summary ASBR Links
    • 19.2.6 - External Links
    • 19.2.7 - The Full Database
• 20.0 - APPENDIX B: OSPF and IP Multicast Addressing
• 21.0 - APPENDIX C: Variable Length Subnet Masks (VLSM)

Section 4:

• OSPF Glossary

Section 5:

• OSPF Q&A