Switch 7700 Configuration Guide

Static Routes 63
The following routes are static routes:
■ Reachable route — The normal route in which the IP packet is sent to the next
hop by the route marked by the destination. It is a common type of static
route.
■ Unreachable route — When a static route to a destination has the reject
attribute, all the IP packets to this destination are discarded, and the originating
host is informed that the destination is unreachable.
■ Blackhole route — When a static route to a destination has the blackhole
attribute, all the IP packets to this destination are discarded, and the originating
host is not informed.
The attributes reject and blackhole are usually used to control the range of
reachable destinations of this router, and to help troubleshoot the network.
Default Route
A default route is a static route, too. A default route is used only when no suitable
routing table entry is found. In a routing table, the default route is in the form of
the route to the network 0.0.0.0 (with the mask 0.0.0.0). You can determine
whether a default route has been set by viewing the output of the display ip
routing-table command. If the destination address of a packet fails to match any
entry of the routing table, the router selects the default route to forward this
packet. If there is no default route and the destination address of the packet fails
to match any entry in the routing table, this packet is discarded, and an Internet
Control Message Protocol (ICMP) packet is sent to the originating host to indicate
that the destination host or network is unreachable.
In a typical network that consists of hundreds of routers, significant bandwidth
would be consumed if you used multiple dynamic routing protocols without
configuring a default route. Using the default route can provide appropriate
bandwidth, though not high bandwidth, for communications between large
numbers of users.
Configuring Static
Routes
Static route configuration tasks are described in the following sections:
■ Configuring a Static Route
■ Configuring a Default Route
Configuring a Static Route
Perform the following configurations in system view.
The parameters are explained as follows:
■ IP address and mask
Tabl e 2 Configure a Static Route
Operation Command
Add a static route ip route-static ip-address {mask | mask-length } {
interface-name | gateway-address } [ preference value ] [
reject | blackhole ]
Delete a static route undo ip route-static ip-address {mask | mask-length } {
interface-name | gateway-address} [ preference value ]