1-2z The network administrator can configure a default route with both destination and mask being0.0.0.0. The router forwards any packet whose destination address fails to match any entry in therouting table to the next hop of the default static route.z Some dynamic routing protocols, such as OSPF, RIP and IS-IS, can also generate a default route.For example, an upstream router running OSPF can generate a default route and advertise it toother routers, which install the default route with the next hop being the upstream router.Application Environment of Static RoutingBefore configuring a static route, you need to know the following concepts:1) Destination address and maskIn the ip route-static command, an IPv4 address is in dotted decimal format and a mask can be eitherin dotted decimal format or in the form of mask length (the digits of consecutive 1s in the mask).2) Output interface and next hop addressWhile configuring a static route, you can specify either the output interface or the next hop addressdepending on the specific occasion. The next hop address can not be a local interface IP address;otherwise, the route configuration will not take effect.In fact, all the route entries must have a next hop address. When forwarding a packet, a router firstsearches the routing table for the route to the destination address of the packet. The system can find thecorresponding link layer address and forward the packet only after the next hop address is specified.When specifying the output interface, note that:z If the output interface is a Null 0 interface, there is no need to configure the next hop address.z If the output interface is a point-to-point interface, there is no need to configure the next hopaddress. You need not change the configuration even if the peer’s address changes. For example,a PPP interface obtains the peer’s IP address through PPP negotiation, so you need only specifythe output interface.z If the output interface is an NBMA or P2MP interface, which support point-to-multipoint network,the IP address to link layer address mapping must be established. Therefore, it is recommended toconfigure both the next hop IP address and the output interface.z You are not recommended to specify a broadcast interface (such as an Ethernet interface, virtualtemplate, or VLAN interface) as the output interface, because a broadcast interface may havemultiple next hops. If you have to do so, you must specify the corresponding next hop for the outputinterface.3) Other attributesYou can configure different preferences for different static routes so that route management policies canbe applied more flexibly. For example, specifying the same preference for different routes to the samedestination enables load sharing, while specifying different preferences for these routes enables routebackup.Configuring a Static RouteConfiguration PrerequisitesBefore configuring a static route, you need to finish the following tasks:z Configure the physical parameters for related interfacesz Configure the link-layer attributes for related interfaces
