OSPF area types

For previous post about LSA types in OSPF...Click here lsa-types-in-ospf

OSPF area types:

1. Backbone area (area 0)
2. Standard area
3. Stub area
4. Totally stubby area
5. Not-so-stubby area (NSSA)

Note: The concept of Areas is to compress the LSA’s. so as to reduce the Traffic in Network.

     Let's begin by examining a standard area. Note that the backbone area is essentially a standard area which has been designated as the central point to which all other areas connect, so a discussion of standard area behavior largely applies to the backbone area as well.

Standard Areas:

LSA Types in OSPF

For previous post about DR and DBR in OSPF...Click here...dr-and-bdr-concepts-in-ospf

LSA Types in OSPF

OSPF relies on several types of Link State Advertisements (LSAs) to communicate link state information between neighbours. A brief review of the most applicable LSA types:

LSA Types:

• Type 1 - Represents a router
• Type 2 – Network LSA (who is my DR)
• Type 3 - A network link summary all ABR (internal route)
• Type 4 - Represents an ASBR (who is my ASBR)
• Type 5 - A route external to the OSPF domain
• Type 6 – Group membership Multicasting
• Type 7 - Used in stub areas in place of a type 5 LSA

DR and BDR Concepts in OSPF

For previous post about Neighbourship formation....Click here neighbour-formation-stages-in-ospf

àIn a network all the router will sends route updates to all other routers, so that the burden is very high on the network due to the routing updates traffic. 

      To solve this DR and BDR is introduced. So that all the routers will send route updates to these DR and BDR only

Ø  To reduce the FULL Neighbourships.

Ø  To reduce the CPU burden on devices.

Ø  To reduce the Bandwidth utilization.

So that all routers will make FULL Neighbourship with DR, while the other router will make up to 2-Way state neghbourship only.