Introduction Hierarchy in OSPF Selecting Area Identifiers There is enough ugliness in the world Basic OSPF Components
Special Considerations for Area 0.0.0.0 Don't Be Seduced by a Single Area 0.0.0.0
Area Sizing
Introducing the ABR A Key Difference between OSPF and ISIS Basic Multiple Area Configuration
Interior Router Configuration
Simple ABR Configuration
More Complex ABR Configuration
Backbone Router Configuration Externals
Introducing the ASBR
Types of Externals
OSPF and Defaults Redistributing Static Default into OSPF Redistributing Default into OSPF from Another Dynamic Routing Protocol Default-Information-Originate Externals from the Internet
Applications of Type 1 and Type 2 Externals Load-Sharing ISP Connection Primary-Backup ISP Connectivity
Hierarchical versus Mutual Importing and Exporting Warning!
LSAs and LSA Propagation Wisdom from fellow ZoneMaster Peter van Oene Summarization and Aggregation
How to Summarize Another Reminder of Different Kinds of Masks
Aggregating Externals
Advertising Holes Area Types: Limiting LSA Propagation
Basic Stub Areas Restrictions of Basic Stub Areas
Totally Stubby Areas and Closest Exit Routing Restrictions of Totally Stubby Areas
Multiple ABR Issues and Asymmetrical Routing
Not-so-stubby Areas Restrictions in NSSAs
The Totally Stubby and Also Not-so-stubby Area Breaking Hierarchy
Manual Traffic Engineering
Tunnels and OSPF GRE Virtual Links Healing Backbone Partitions across a Non-OSPF Domain Linking Disconnected Areas Learning More