Open Shortest Path First (OSPF)
OSPF Introduction
- Open standard
- Cisco proprietary - vs. 3rd part
- Routers, switches, firewalls, load balancers, WLCs, etc
- Windows, Linux, BSD, OSX
Open Shortest Path First
- Link-state
- Build a map
- Calculate the path
- Using Dijkstra algorithm
- When there is changes on the path, things constantly going up and down.
- Everyone recalculates best path again
- Everytime this happnes the router has to do a lot of work to reestablish a path for everyone.
- Scalable
- Multi-area
- OSPF is big enough to scale to areas
- When there is a problem we can isolate it to a smaller group
- Tunable
Steps of OSPF
- Enabled per interface
- Neighbor relationships
- Link-state database
- Dijkstra algorithm
- Responsible for calculating the shortest path first
- Also used by the mapping system (GPS, google maps, etc.)
- Optimal paths
- Every single router running OSPF considers itself as the center of the universe
- Optimal paths are pushed to Routing Information Base (RIB)
- Administrative distance
- Every router information has a different value to it.
- Still competing with things like Static route, direct, etc...
OSPF Sample Configuration
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- The middle one is EXACT
- Only want to do OSPF in the interface with this exact IP
- The bottom one is running EVERYWHERE
- Include any interface that I have
- Kind of like the autopilot
- The downside is that it will include everything that you have, but maybe you want to keep some things out of OSPF