Routing Management Policy - 3Com 8807 Configuration Manual

282 C 28: IP R
HAPTER OUTING
Routing Management
Policy
Routing Protocols and
the Preferences of the
Corresponding Routes
Supporting Load
Sharing and Route
Backup
P O
ROTOCOL VERVIEW
addition, the running switch will automatically obtain some direct routes
according to the port state and user configuration.
For Switch 8800 Family series, you can configure manually the static route to a
specific destination, and configure dynamic routing protocol to interact with other
routers on the network. The routing algorithm can also be used to discover routes.
For the configured static routes and dynamic routes discovered by the routing
protocol, the Switch 8800 Family series implement unified management. That is,
the static routes configured by the user are managed together with the dynamic
routes discovered by the routing protocol. The static routes and the routes learned
or configured by different routing protocols can also be shared with each other.
Different routing protocols (as well as the static configuration) may 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 specific destination. Thus, each of these routing protocols (including the static
configuration) is set with a preference, and when there are multiple routing
information sources, the route discovered by the routing protocol with the highest
preference will become the current route. Routing protocols and the default
preferences (the smaller the value is, the higher the preference is) of the routes
learned by them are shown in Table 248.
In the table, 0 indicates a direct route. 255 indicates any route from unreliable
sources.
Table 248 Routing protocols and the default preferences for the routes learned by them
Routing protocol or route type
DIRECT
OSPF
IS-IS
STATIC
RIP
OSPF ASE
OSPF NSSA
IBGP
EBGP
UNKNOWN
Apart from direct routing, 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.
Load sharing
The Switch 8800 Family series support static equivalent route, permitting to
configure multiple routes that reach the same destination and use the same
precedence. After you configured static equivalent routes, a packet can reach the
same destination through multiple different paths, whose precedence levels are
equal. When there is no route that can reach the same destination with a higher
The preference of the corresponding route
0
10
15
60
100
150
150
256
256
255