Why is a backbone area Area 0 required for OSPF?
An OSPF routing domain (AS) can consist of a single area, but in that case the single area must be Area 0. Only the backbone area can generate the summary routing topology information that is used by the other areas. This is why all interarea traffic must pass through the backbone area.
What is the best definition of the use of Area 0 in OSPF?
All OSPF networks have at least one area with the default being area 0. If more than one area exists, area 0 is defined as the backbone area and is used to connect all other areas. External routes refer to updates passed from another routing protocol into the OSPF domain by the Autonomous System Border Router (ASBR).
Can you have OSPF without Area 0?
Is it possible? YES! Only if you use one and only one area.
Which is the backbone area in OSPF protocol?
The choice of OSPF protocol designers is clear: in a multi area domain the backbone area is the center and all other areas have to connect to it. By enforcing this design rule some issues that could be caused by the way the inter area routing information is generated are solved.
How are area 0 and R1 connected in OSPF?
R1 (Area 5 ABR), is connected to Area 0; it translates the Type1 LSA into a Type3 LSA with a cost of 3. R2 (Area 4 ABR) receives R1’s Type3 LSA (metric 3) and changes the metric to R5’s Loopback, based on R2’s cost to R1.
How are OSPF networks divided into sub-domains?
An OSPF network can be divided into sub-domains called areas. An area is a logical collection of OSPF networks, routers, and links that have the same area identification. A router within an area must maintain a topological database for the area to which it belongs. The router does not have detailed information about network topology outside
Which is an ABR for R5 in OSPF?
R5 is member of area 3 and it has a direct connection to R3 that is a valid ABR and injects into area 3 summary LSAs for all existing areas: 0,4,5, For this reason R5 has routes for links between R1 and R2. You can visualize the OSPF multi-area rules as a daisy flower with area 0 that is the center of the flower and the other areas are the petals.