OSPF Path Selection With Non Backbone Transit Areas

OSPF Path Selection with Non-Backbone Transit Areas
Transit Capability

• OSPF area transit capability as the ability of the area to carry data traffic that neither originates nor terminates in the area itself.
• OSPF ABR to discover shorter path from the transit area then forward traffic along those paths prefer over other paths
• Usually routers always prefer the route transit through area 0 even though other shortest paths available without transiting through  area 0. By enabling transit capability which is default feature, it choose the shortest path through non backhone area.

Enable Transit Capability

CONFIGURATION
R1 (config) # router ospf 1
R1 (config-router) # area 1 virtual-link 150.1.6.6
R1 (config-router) # no capability transit

R6 (config) # router ospf 1
R6 (config-router) # area 1 virtual-link 150.1.1.1
R6 (config-router) # no capability transit


Disable Transit Capability 
After applying configuration, R6 choose R1,

  

Reference 

INE LAB OSPF PATH SELECTION