26 STATIC ROUTING CONFIGURATIONWhen configuring a static route, go to these sections for information you areinterested in:■ “Introduction” on page 251■ “Configuring a Static Route” on page 252■ “Application Environment of Static Routing” on page 252■ “Displaying and Maintaining Static Routes” on page 254■ “Configuration Example” on page 254n The term “router” in this document refers to a router in a generic sense or a Layer3 switch.IntroductionStatic Route A static route is a special route that is manually configured by the networkadministrator. If a network’s topology is simple, you only need to configure staticroutes for the network to work normally. The proper configuration and usage ofstatic routes can improve network performance and ensure bandwidth forimportant network applications.The disadvantage of using static routes is that they cannot adapt to networktopology changes. If a fault or a topological change occurs in the network, theroutes will be unreachable and the network breaks. In this case, the networkadministrator has to modify the static routes manually.Default Route A router selects the default route only when it cannot find any matching entry inthe routing table.If the destination address of a packet fails to match any entry in the routing table,the router selects the default route to forward the packet.If there is no default route and the destination address of the packet fails to matchany entry in the routing table, the packet will be discarded and an ICMP packetwill be sent to the source to report that the destination or the network isunreachable.You can create the default route with both destination and mask being 0.0.0.0,and some dynamic routing protocols, such as OSPF, RIP and IS-IS, can alsogenerate the default route.
