Links:
Backbone area (Area 0)
Let’s start with the Backbone area. The backbone area is just as the name implies the backbone of the OSPF domain. Think of the backbone area as the hub for OSPF. The backbones main responsibility is to distribute routing information (LSAs) between non-backbone areas.Breakdown of Backbone Area:
- Backbone = area 0 (or area 0.0.0.0)
- Must be contiguous and not split up
- All area ABRs must connect to the backbone
- Virtual links are used when areas are not physically connected
- Cannot be configured as stub or NSSA area type
- Redistribution allowed into the backbone area
- All LSA types are allowed and propagated