Static Routes - 3Com Switch 4500 26-Port Configuration Manual

106 C 6: IP R P O
HAPTER OUTING ROTOCOL PERATION
Supporting Load Sharing and Route Backup
I. Load sharing
The Switch 4500 supports multi-route mode, allowing the user to configure
multiple routes that reach the same destination and use the same precedence. The
same destination can be reached via multiple different paths, whose precedences
are equal. When there is no route that can reach the same destination with a
higher precedence, the multiple routes will be adopted by IP, which will forward
the packets to the destination via these paths so as to implement load sharing.
For the same destination, a specified routing protocol may find multiple different
routes. If the routing protocol has the highest precedence among all active routing
protocols, these multiple routes will be regarded as currently valid routes. Thus,
load sharing of IP traffic is ensured in terms of routing protocols.
The Switch 4500 supports three routes to implement load sharing.
II. Route backup
The Switch 4500 supports route backup. If the main route is in failure, the unit will
automatically switch to a backup route to improve the network reliability.
To achieve route backup, the user can configure multiple routes to the same
destination according to actual situation. One of the routes has the highest
precedence and is called the main route. The other routes have descending
precedences and are called backup routes. Normally, the router sends data via the
main route. When the line fails, the main route will hide itself and the router will
choose from one of the remaining routes as a backup route whose precedence is
higher than the others to send data. This process is the switchover from the main
route to the backup route. When the main route recovers, the router will restore it
by re-selecting the main route. As the main route has the highest precedence, the
router will select the main route again to send data. This process is the automatic
switchover from the backup route to the main route.
Routes Shared between Routing Protocols
As the algorithms of various routing protocols are different, different protocols can
generate different routes. This situation creates the problem of how to resolve the
different routes being generated by different routing protocols. The Switch 4500
can import the information of another routing protocol. Each protocol has its own
route redistribution mechanism. For more information, see "Configuring RIP to
Import Routes of Other Protocols" on page 117.

Static Routes

A static route is a route that is manually configured by the network administrator.
You can set up an interconnected network using static routes. However, if a fault
occurs in the network, the static route cannot change automatically to steer
packets away from the fault without the help of the administrator.
In a relatively simple network, you only need to configure static routes to make the
router work normally. Proper configuration and usage of the static route can
improve network performance and ensure bandwidth for important applications.