Dell BigIron RX Series, Руководство по настройке

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712 BigIron RX Series Configuration Guide
53-1002253-01
Configuring OSPF
25
Modify administrative distance
The BigIron RX can learn about networks from various protocols, including Border Gateway Protocol
version 4 (BGP4), RIP, ISIS, and OSPF. Consequently, the routes to a network may differ depending
on the protocol from which the routes were learned. The default administrative distance for OSPF
routes is 110. Refer to
“Changing administrative distances” on page 767 for a list of the default
distances for all route sources.
The router selects one route over another based on the source of the route information. To do so,
the router can use the administrative distances assigned to the sources. You can bias the device’s
decision by changing the default administrative distance for OSPF routes.
Configuring administrative distance based on route type
You can configure a unique administrative distance for each type of OSPF route. For example, you
can use this feature to prefer a static route over an OSPF inter-area route but you also want to
prefer OSPF intra-area routes to static routes.
The distance you specify influences the choice of routes when the device has multiple routes for
the same network from different protocols. The device prefers the route with the lower
administrative distance.
You can specify unique default administrative distances for the following route types:
•
Intra-area routes
•
Inter-area routes
•
External routes
The default for all these OSPF route types is 110.
NOTE
This feature does not influence the choice of routes within OSPF. For example, an OSPF intra-area
route is always preferred over an OSPF inter-area route, even if the intra-area route’s distance is
greater than the inter-area route’s distance.
To change the default administrative distances for inter-area routes, intra-area routes, and external
routes, enter the following command.
BigIron RX(config-ospf-router)# distance external 100
BigIron RX(config-ospf-router)# distance inter-area 90
BigIron RX(config-ospf-router)# distance intra-area 80
Syntax: distance external | inter-area | intra-area <distance>
The external | inter-area | intra-area parameter specifies the route type for which you are changing
the default administrative distance.
The <distance> parameter specifies the new distance for the specified route type. Unless you
change the distance for one of the route types using commands such as those shown above, the
default is 110.
To reset the administrative distance to its system default (110), enter a command such as the
following.
BigIron RX(config-ospf-router)# no distance external 100