Switch 7700 Configuration Guide

62 CHAPTER 5: ROUTING PROTOCOL OPERATION
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
Tabl e 1.
In the table, 0 indicates a direct route, 255 indicates any route from an unreliable
source.
Except for direct routing and BGP (IBGP and EBGP), the preferences of various
dynamic routing protocols can be manually configured to meet the user
requirements. In addition, 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 7700
supports an operation of importing the routes generated by one routing protocol
into another routing protocol. Each protocol has its own route redistribution
mechanism. For details, refer to
“Configure RIP to Import Routes of Other
Protocols”, “Configure OSPF to Import the 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 interconnecting network with the static route configuration.
However, when a fault occurs to the network, the static route cannot change
automatically to steer packets away from the node causing the fault without the
help of an 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 the network performance and ensure the bandwidth of the important
applications.
Tab le 1 Routing Protocols and the Default Preferences for Routes
Routing protocol or route type The preference of the corresponding route
DIRECT 0
OSPF 10
STATIC 60
RIP 100
OSPF ASE 150
OSPF NSSA 150
IBGP 256
EBGP 256
UNKNOWN 255