OSPF Q & A

1: What is an OSPF neighbor?

*** From the perspective of an OSPF router, a neighbor is another OSPF router that is attached to one of the first router's directly connected links.


2: What is an OSPF adjacency?

***An OSPF adjacency is a conceptual link to a neighbor over which LSAs can be sent.

3: What is an LSA? How does an LSA differ from an OSPF Update packet?


***A router originates a link state advertisement to describe one or more destinations. An OSPF Update packet transports LSAs from one neighbor to another. Although LSAs are flooded throughout an area or OSPF domain, Update packets never leave a data link.

4: What is a link state database? What is link state database synchronization?

***The link state database is where a router stores all the OSPF LSAs it knows of, including its own. Database synchronization is the process of ensuring that all routers within an area have identical link state databases.

5: What is the default HelloInterval?

***The default OSPF HelloInterval is 10 seconds.

6: What is the default RouterDeadInterval?

***The default RouterDeadInterval is four times the HelloInterval.

7: What is a Router ID? How is a Router ID determined?

***A Router ID is an address by which an OSPF router identifies itself. It is either the numerically highest IP address of all the router's loopback interfaces, or if no loopback interfaces are configured, it is the numerically highest IP address of all the router's LAN interfaces.


8: What is an area?

***An area is an OSPF sub-domain, within which all routers have an identical link state database.

9: What is the significance of area 0?

***Area 0 is the backbone area. All other areas must send their inter-area traffic through the backbone.

10: What is MaxAge?

***MaxAge, 1 hour, is the age at which an LSA is considered to be obsolete.