LSAs cause every router within the area to recalculate routes. Because LSAs
need to be ?¬‚ooded throughout an area and all routers within that area need to recalculate their
routing tables, you should limit the number of link-state routers that can be in an area.
A link is similar to an interface on a router. The state of the link is a description of that interface
and of its relationship to its neighboring routers. A description of the interface would include, for
example, the IP address of the interface, the mask, the type of network to which it is connected,
the routers connected to that network, and so on. The collection of link states forms a link-state,
or topological, database. The link-state database is used to calculate the best paths through the
network. Link-state routers ?¬?nd the best paths to a destination by applying Dr. Edsger Dijkstra??™s
SPF algorithm against the link-state database to build the SPF tree. The best paths are then selected
from the SPF tree and placed in the routing table.
Reviewing Dynamic Routing 117
As networks become larger in scale, link-state routing protocols become more attractive for the
following reasons:
?– Link-state protocols always send updates when a topology changes.
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