3Com 7757 Configuration Manual page 284

284 C 31: IP R P O
HAPTER OUTING ROTOCOL VERVIEW
Except for direct routing, you can manually configure the preferences of various
dynamic routing protocols as required. In addition, you can configure different
preferences for different static routes.
Traffic Sharing and Traffic sharing
Route Backup
The Switch 7750 support multi-route mode, allowing the configuration of multiple
routes that reach the same destination and have the same preference. The same
destination can be reached via multiple different routes, whose preferences are
equal. When there is no route with a higher preference to the same destination,
the multiple routes will be adopted. Then, the packets destined for the same
destination will be forwarded through these routes in turn to implement traffic
sharing.
Route backup
The Switch 7750 support route backup. When the main route fails, the system
automatically switches to a backup route to improve network reliability.
To achieve route backup, you can configure multiple routes to the same
destination according to actual situation. One of the routes has the highest
preference and is called primary route. The other routes have descending
preferences and are called backup routes. Normally, the router sends data through
the main route. When line failure occurs on the main route, the main route will
hide itself and the router will choose the one whose preference is the highest
among the remaining backup routes as the path to send data. In this way, the
switchover from the main route to a backup route is implemented. When the main
route recovers, the router will restore it and re-select a route. And, as the main
route has the highest preference, the router will choose the main route to send
data. This process is the automatic switchover from the backup route to the main
route.
Routes Shared Between As the algorithms of various routing protocols are different, different routing
Routing Protocols protocols may discover different routes. This brings about the problem of how to
share the discovered routes between routing protocols. The Switch 7750 can
import (with the import-route command) the routes discovered by one routing
protocol to another routing protocol. Each protocol has its own route
redistribution mechanism. For detailed information, refer to "Importing Routes"
on page 357.