3Com 4800G Series, Configuration Manual

Page: 251 / 1246

26
S
TATIC
R
OUTING
C
ONFIGURATION
When configuring a static route, go to these sections for information you are
interested 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 254
n
The term “router” in this document refers to a router in a generic sense or a Layer
3 switch.
Introduction
Static Route A static route is a special route that is manually configured by the network
administrator. If a network’s topology is simple, you only need to configure static
routes for the network to work normally. The proper configuration and usage of
static routes can improve network performance and ensure bandwidth for
important network applications.
The disadvantage of using static routes is that they cannot adapt to network
topology changes. If a fault or a topological change occurs in the network, the
routes will be unreachable and the network breaks. In this case, the network
administrator has to modify the static routes manually.
Default Route A router selects the default route only when it cannot find any matching entry in
the 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 match
any entry in the routing table, the packet will be discarded and an ICMP packet
will be sent to the source to report that the destination or the network is
unreachable.
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 also
generate the default route.