What information does a router running a link-state protocol use to build and maintain its topological database? (Choose two.)
A . hello packets
B . SAP messages sent by other routers
C . LSAs from other routers
D . beacons received on point-to-point links
E . routing tables received from other link-state routers
F . TTL packets from designated routers
Answer: A,C
Explanation:Link State Routing Protocols
http://www.ciscopress.com/articles/article.asp?p=24090&seqNum=4
Link state protocols, sometimes called shortest path first or distributed database protocols, are built around a well-known algorithm from graph theory, E. W. Dijkstra’a shortest path algorithm. Examples of link state routing protocols are: Open Shortest Path First (OSPF) for IP The ISO’s Intermediate System to Intermediate System (IS-IS) for CLNS and IP DEC’s DNA Phase V Novell’s NetWare Link Services Protocol (NLSP) Although link state protocols are rightly considered more complex than distance vector protocols, the basic functionality is not complex at all:
Each router establishes a relationship―an adjacency―with each of its neighbors.
Each router sends link state advertisements (LSAs), some
Each router stores a copy of all the LSAs it has seen in a database. If all works well, the databases in all routers should be identical.
The completed topological database, also called the link state database, describes a graph of the internetwork. Using the Dijkstra algorithm, each router calculates the shortest path to each network and enters this information into the route table.