in larger, more complicated networks or in networks that must be highly scalable.
and resources are required to support link-state routing than distance-vector routing. The cost
of the routers that are configured for link-state routing is higher. These issues are not
showstoppers and are easy to overcome with foresight, planning, and good design. OSPF, an
example of a link-state protocol, uses cost as a metric.
than conventional distance-vector protocols. They also converge more rapidly than distance-
vector protocols but avoid the overhead of link-state updates. Balanced hybrids are event-driven
rather than periodic and thereby conserve bandwidth for real applications.
Enhanced Interior Gateway Routing Protocol (EIGRP). EIGRP was designed to combine the
best characteristics of both routing protocols without incurring any of their performance
limitations or penalties. EIGRP finds new networks like a distance-vector protocol while
reacting to changes in topology like a link-state routing protocol.
tables built? When more than one route is available, how do protocols select a preferred route?
Routing protocols use metrics to determine the best route. The following metrics can be used
to determine the
best route:
The cost metric is the sum of the costs associated with each link traversed.
take to get from source to destination.
network links might go down more often than others. After a network fails, certain
network links might be repaired more easily or more quickly than others. Any factors that
govern reliability can be factored into the reliability metric.
destination. Several factors affect delay, including the bandwidth of intermediate network
links, the port queues at each router along the way, network congestion, and the physical
distance to be traveled.