3Com Switch 8800 Configuration Guide Chapter 17 Static Route Configuration17-1Chapter 17 Static Route Configuration17.1 Introduction to Static Route17.1.1 Static RouteA static route is a special route configured manually by an administrator. You can set upan interconnecting network with the static route configuration. The problem for suchconfiguration is when a fault occurs to the network, the static route cannot changeautomatically to steer away from the node causing the fault, if without the help of anadministrator.In a relatively simple network, you only need to configure the static routes to make therouter work normally. The proper configuration and usage of the static route canimprove the network performance and ensure the bandwidth of the importantapplications.All the following routes are static routes:z Reachable route: A normal route is of this type. That is, the IP packet is sent to thenext hop via the route marked by the destination. It is a common type of staticroutes.z Unreachable route: When a static route to a destination has the "reject" attribute,all the IP packets to this destination will be discarded, and the source host will beinformed that the destination is unreachable.z Blackhole route: If a static route to a destination has the “blackhole” attribute, theoutgoing interface of this route is the Null 0 interface regardless of the next hopaddress, and any IP packets addressed to this destination are dropped withoutnotifying the source host.The attributes "reject" and "blackhole" are usually used to control the range ofreachable destinations of this router, and help troubleshooting the network.17.1.2 Default RouteA default route is a special route. You can configure a default route using a static route.Some dynamic routing protocols can also generate default routes, such as OSPF andIS-IS.In brief, a default route is used only when no suitable routing table entry is matched.That is, when no proper route is found, the default route is used. In a routing table, thedefault route is in the form of the route to the network 0.0.0.0 (with the mask 0.0.0.0).You can see whether the default route has been set by executing the display iprouting-table command. If the destination address of a packet fails in matching anyentry of the routing table, the router will select the default route to forward this packet. If
