Static and Dynamic IP Routers

For IP routing between routers to occur efficiently in the IP internetwork, routers must have explicit knowledge of remote network IDs or be properly configured with a default route. On large IP internetworks, one of the challenges faced by network administrators is how to maintain the routing tables on their IP routers so that IP traffic flow is traveling the best path and is fault tolerant.

There are two ways of maintaining routing table entries on IP routers:

• Manually—Static IP routers have routing tables that do not change unless manually changed by a network administrator.
  Static routing relies on the manual administration of the routing table. Remote network IDs are not discovered by static routers and must be manually configured. Static routers are not fault tolerant. If a static router goes down, neighboring routers do not sense the fault and inform other routers.

• Automatically—Dynamic IP routers have routing tables that change automatically based on the communication of routing information with other routers.
  Dynamic routing employs the use of routing protocols, such as Routing Information Protocol (RIP) and Open Shortest Path First (OSPF), to dynamically update the routing table through the exchange of routing information between routers. Remote network IDs are discovered by dynamic routers and automatically entered into the routing table. Dynamic routers are fault tolerant. If a dynamic router goes down, the fault is sensed by neighboring routers who propagate the changed routing information to the other routers in the internetwork.

For more information about routing principles, see "Unicast Routing Overview" in the Windows   2000InternetworkingGuide . For more information about IP routing protocols, see "Unicast IP Routing" in the Windows   2000InternetworkingGuide .