3Com Switch 8800 Configuration Guide
Chapter 17 Static Route Configuration
17-1
Chapter 17 Static Route Configuration
17.1 Introduction to Static Route
17.1.1 Static Route
A static route is a special route configured manually by an administrator. You can set up
an interconnecting network with the static route configuration. The problem for such
configuration is when a fault occurs to the network, the static route cannot change
automatically to steer away from the node causing the fault, if without the help of an
administrator.
In a relatively simple network, you only need to configure the static routes to make the
router work normally. The proper configuration and usage of the static route can
improve the network performance and ensure the bandwidth of the important
applications.
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 the
next hop via the route marked by the destination. It is a common type of static
routes.
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 be
informed that the destination is unreachable.
z
Blackhole route: If a static route to a destination has the “
blackhole
” attribute, the
outgoing interface of this route is the Null 0 interface regardless of the next hop
address, and any IP packets addressed to this destination are dropped without
notifying the source host.
The attributes "
reject
" and "
blackhole
" are usually used to control the range of
reachable destinations of this router, and help troubleshooting the network.
17.1.2 Default Route
A 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 and
IS-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, 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 see whether the default route has been set by executing the
display ip
routing-table
command. If the destination address of a packet fails in matching any
entry of the routing table, the router will select the default route to forward this packet. If
