3Com 10014298 manual Static Routes, Unreliable source, Individual static routes can be different

84CHAPTER 5: IP ROUTING PROTOCOL OPERATION

user are managed together with the dynamic routes as detected by the routing protocol. The static routes and the routes learned or configured by routing protocols can be shared with each other.

Routing protocols (as well as the static configuration) can generate different routes to the same destination, but not all these routes are optimal. In fact, at a certain moment, only one routing protocol can determine a current route to a single destination. Thus, each routing protocol (including the static configuration) has a set preference, and when there are multiple routing information sources, the route discovered by the routing protocol with the highest preference becomes the current route. Routing protocols and the default preferences (the smaller the value, the higher the preference) of the routes that they learn are shown in Table 78.

Table 78 Routing Protocols and the Default Preferences for Routes

Routing protocol or route type	The preference of the corresponding
	route
DIRECT	0
STATIC	60
RIP	100
UNKNOWN	255

	In the table, 0 indicates a direct route, and 255 indicates any route from an
	unreliable source.
	Except for direct routing, the preferences of various dynamic routing protocols can
	be manually configured to meet the user requirements. The preferences for
	individual static routes can be different.
	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
	different routes being generated by different routing protocols. The Switch 7750
	supports an operation to import the routes generated by one routing protocol into
	another routing protocol. Each protocol has its own route redistribution
	mechanism. For details, refer to “Enabling RIP to Import Routes of Other
	Protocols”, or “Importing Routing Information Discovered by Other Routing
	Protocols”.
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. The proper configuration and usage of the static route can
	improve network performance and ensure bandwidth for important applications.

The following routes are static routes:

■Reachable route — The normal route in which the IP packet is sent to the next hop towards the destination. this is a common type of static route.