Static Routes - 3Com Switch 7700 Configuration Manual

90 C 5: IP R
HAPTER OUTING

Static Routes

P O
ROTOCOL PERATION
the 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 1.
Table 1 Routing Protocols and the Default Preferences for Routes
Routing protocol or route type
DIRECT
OSPF
ISIS
STATIC
RIP
OSPF ASE
OSPF NSSA
IBGP
EBGP
UNKNOWN
In the table, 0 indicates a direct route, and 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. 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 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", "Configuring OSPF to Import the Routes of Other Protocols", or
"Importing Routing Information Discovered by Other Routing Protocols".
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.
The preference of the corresponding
route
0
10
15
60
100
150
150
256
256
255