OSPF

OSPF Area types

Configuration of OSPF gives us a choice between 5 different areatypes:

  • Normal
  • Stub
  • Totally Stub
  • Not So Stubby Area
  • Totally Not So Stubby Area (omg what a name?!)

To just list all the different types and behavior would not give the reader much help, it would just be confusing, so I decided to break it down the same way i did to learn it myself.

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OSPF and virtual links

Background;
Area 0 is the only backbone area in ospf, all areas needs to be connected via some ABR to Area 0 in order to be routed to another area. For example:

Area 1 —Router1—Area 0—Router2—Area 2—Router3—Area3

Here will all routers act as Area Border Routers, R1 will be the ABR for areas 1 and 0. Router 2 will be the ABR for areas 0 and 2.
Router3 will be the ABR between areas 2 and 3… ? 

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OSPF traffic manipulation with bandwidth

Task: Make sure traffic to 10.100.123.0/24 uses the path via R2 by changing the bandwidth

 

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Interarea routing and path selection with OSPF

What path does OSPF choose to a specific destination?

Recently when I have been labbing OSPF more than before I noticed I stumbled when verifying the path ospf chooses for a specific destination. Lets look for instance at the topology here. First lets see with ospf database commands which path the routers uses and why, then how we can manipulate this.

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