Advanced OSPF - Areas

10 important questions on Advanced OSPF - Areas

What is an OSPF Area?

An OSPF Area is a logical collection of networks, routes and links that have the same area identification.

What is an important rule when dividing an OSPF network in multiple areas?

The OSPF area 0 always is the backbone area. Any other OSPF area must be connected to the backbone area.

What three things happen when designating an area as a Stub Area?

1. The ABR advertises itself as the default route using an LSA Type 3.
2. The ABR will not forward any LSA Type 5 into the area.
3. Because of no LSA Type 5 LSAs there won't be any LSA Type 4 LSAs.
  • Higher grades + faster learning
  • Never study anything twice
  • 100% sure, 100% understanding
Discover Study Smart

Why would a Stub Area be useful?

It prevents unneccesary LSA Type 4 and Type 5 messages because the Stub Area only has one breakout through the ABR.

What is a Totally Stub Area?

It is an OSPF Area where the ABR is configured to stop sending LSA Type 3 LSAs using the No-Summary command.
This way the area will only know about it's own networks and have a default route to the ABR.

What is a Not So Stubby Area (NSSA) and why is it used?

In a Stub area there can't be any ASBRs because LSA type 5 are not allowed. A NSSA is a Stub area where ASBRs are allowed, however the routes are propagated using LSA Type 7 instead of Type 5.

What is the benefit of using a Totally Not So Stubby Area?

Just like a Totally Stub Area, it prevents it from creating LSA Type 3 LSAs.

How many LSDBs does an ABR have?

One for each Area it is participating in.

What is the OSPF Area ID?

It is a 32-bit field which can be written in simple decimal and dotted decimal (4 octects).

What are two different route types in OSPF?

1. Intra-Area routes, learned from routers in the same area. Displayed in the Routing Table with an O
2. Inter-Area routes, learned from routers in a different Area using an ABR. Displayed in the Routing Table with an O IA.

The question on the page originate from the summary of the following study material:

  • A unique study and practice tool
  • Never study anything twice again
  • Get the grades you hope for
  • 100% sure, 100% understanding
Remember faster, study better. Scientifically proven.
Trustpilot Logo