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Routing is the process that a router uses
to forward packets toward the destination network. A router makes
decisions based upon the destination IP address of a packet. All
devices along the way use the destination IP address to point the
packet in the correct direction so that the packet eventually arrives
at its destination. In order to make the correct decisions, routers
must learn the direction to remote networks. When routers use dynamic
routing, this information is learned from other routers. When static
routing is used, a network administrator configures information about
remote networks manually. Because static routes must be
configured manually, any network topology changes require the network
administrator to add and delete static routes to account for the
changes. In a large network this manual maintenance of routing tables
could require a tremendous amount of administrative time. On small
networks with few possible changes, static routes require very
little maintenance. Because of the extra administrative requirements,
static routing does not have the scalability of dynamic routing. Even
in large networks, static routes that are intended to
accomplish a specific purpose are often configured in conjunction
with a dynamic routing protocol.
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