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19 Cards in this Set

  • Front
  • Back
single area is becoming overpowered if: (3)
■ The SPF algorithm is running more frequently.
■ The larger the area, the greater the size of the routing table
■ The topological database increases in size and eventually becomes unmanageable
different OSPF routers:
■ Internal router
■ Backbone router
what are the responsibilities of the internal router?
responsible for maintaining a current and accurate database of every subnet within the area
what is the design rule for the backbone router in OSPF?
The design rules for OSPF require that all the areas be connected through a single area, known as the backbone area, Area 0, or
what are the responsibilities of the ABR?
responsible for connecting two or more areas. It holds a full topological database for each area to which it is connected and sends LSA updates between the areas.
what are the responsibilities of the ASBR?
To connect to the outside world or to any other routing protocol,
OSPF is an EGP / IGP?
If any routing protocols are being redistributed to OSPF on a router, the router will become an
Five commonly used types of link-state advertisements are:
■ The router link LSA (Type 1)
■ The network link LSA(Type 2)
■ The network summary link LSA (Type 3)
■ The AS external ASBR summary link LSA (Type 4)
■ The external link LSA (Type 5)
■ The NSSA external LSA (Type 7)
The Different Types of Areas
■ An ordinary or standard area
■ A stub area
■ A totally stubby area
■ The backbone area
what is a standard area?
This type of area connects to the backbone.
what is a stub area?
This is an area that will not accept external summary routes. The LSA that is
blocked is Type 5. The consequence is that the only way that a router within the stub area can see outside the autonomous system is by the use of a default route.
what is a totally stubby area
This area does not accept summary LSAs from the other areas or the external summary LSAs from outside the autonomous system. The LSAs blocked are Types 3,4, and 5. The only way out of the totally stubby area is via a default route.
what is an a NSSA
This area is used primarily to connect to ISPs, or when redistribution is required.
In most respects, it is the same as the stub area. External routes are not propagated into or out of the area. It does not allow Type 4 or Type 5 LSAs.
What are the restrictions governing creating a stub area or a totally stubby area?
■ No external routes are allowed.
■ No virtual links are allowed.
■ No redistribution is allowed.
■ No ASBR routers are allowed.
■ The area is not the backbone area.
■ All the routers are configured to be stub routers.
Routes generated within an area are Type ___ or Type ___, and these are injected as Type
___ summaries into the backbone.
What are the conditions that need to be met before any LSAs can be flooded out of all interfaces?
■ The LSA was not received through the interface.
■ The interface is in a state of exchange or full adjacency.
■ The interface is not connected to a stub area (no LSA Type 5 will be flooded).
■ The interface is not connected to a totally stubby area (no Type 3, 4, or 5 will be propagated).
The OSPF routing table that exists on a router depends on the following factors:
■ The position that the router has in the area and the status of the network
■ The type of area in which the router is located
■ Whether there are multiple areas in the domain
■ Whether there are communications outside the autonomous system
The router will process the LSAs in which order?
1. The internal LSA (Type 1 and 2).
2. The LSAs of the AS (Type 3 and 4). If there is a route to the chosen network within the area (Type 1 or 2), this path will be kept.
3. The external LSAs (Type 5).