Hierarchical Network Design Techniques
When designing your OSPF network, the following factors are supported by OSPF and are currently accepted network design theories:
- A three-tiered backbone approach allows fast convergence and economy of scale.
- Never use more than six router hops from source to destination (see the following note).
- Use 30 to 100 routers per area. (This can be adjusted depending on factors discussed later.)
- Do not allow more than two areas per Area Border Router (ABR) in addition to the ABR's connection to area 0. Otherwise, the ABR must keep track of too many linkstate databases.
NOTE The Cisco Systems network recommends that you have no more than six hops from source to destination when designing a hierarchical enterprise network. This has some validity; however, in practice, the number of hops you can see depends on what a network is trying to accomplish. Large, long-haul international networks by nature have more than six hops.
In this tutorial:
- OSPF Basics
- What Is a Routing Protocol?
- Basic Routing Protocol Operation
- Link-State Versus Distance Vector Routing Protocols
- Link-State Routing Protocols
- OSPF Characteristics
- Integrated Intermediate System-to-Intermediate System
- Distance Vector Routing Protocols
- Selecting a Routing Protocol
- Operational Considerations
- Protocols Supported
- Routing Hierarchies
- IP Address Management
- IP Encapsulation Support
- Technical Considerations
- Routing Updates
- Scalability
- Business Considerations
- SPF Overview
- OSPF Routing Hierarchy
- Hierarchical Network Design Techniques
- Routing Types Within an OSPF Network
- External Routes
- OSPF Areas
- Characteristics of a Standard OSPF Area
- Stub Areas
- Not-So-Stubby Areas
- OSPF Operational Environment
- Types of OSPF Routers
- OSPF Network Types
- Router Identification
- Neighbors
- Adjacencies