Dell BigIron RX Series, Руководство по настройке

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766 BigIron RX Series Configuration Guide
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Changing the default local preference
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BigIron RX(config-bgp)# default-information-originate
Syntax: [no] default-information-originate
Changing the default local preference
When the router uses the BGP4 algorithm to select a route to send to the IP route table, one of the
parameters the algorithm uses is the local preference. Local preference is an attribute that
indicates a degree of preference for a route relative to other routes. BGP4 neighbors can send the
local preference value as an attribute of a route in an UPDATE message.
Local preference applies only to routes within the local AS. BGP4 routers can exchange local
preference information with neighbors who also are in the local AS, but BGP4 routers do not
exchange local preference information with neighbors in remote ASs.
The default local preference is 100. For routes learned from EBGP neighbors, the default local
preference is assigned to learned routes. For routes learned from IBGP neighbors, the local
preference value is not changed for the route.
When the BGP4 algorithm compares routes on the basis of local preferences, the route with the
higher local preference is chosen.
NOTE
To set the local preference for individual routes, use route maps. Refer to “Defining route maps” on
page 801. Refer to “How BGP4 selects a path for a route” on page 740 for information about the
BGP4 algorithm.
To change the default local preference to 200, enter the following command.
BigIron RX(config-bgp)# default-local-preference 200
Syntax: default-local-preference <num>
The <num> parameter indicates the preference and can be a value from 0 – 4294967295.
Changing the default metric used for redistribution
The BigIron RX can redistribute directly connected routes, static IP routes, RIP routes, ISIS routes,
and OSPF routes into BGP4. By default, BGP uses zero (0) for direct connected routes and the
metric (MED) value of IGP routes in the IP route table. The MED is a global parameter that specifies
the cost that will be applied to all routes, if assigned, when they are redistributed into BGP4. When
routes are selected, lower metric values are preferred over higher metric values. The default, the
BGP4 MED value is not assigned.
NOTE
RIP, ISIS, and OSPF also have default metric parameters. The parameters are set independently for
each protocol and have different ranges.
To change the default metric to 40, enter the following command.
BigIron RX(config-bgp)# default-metric 40
Syntax: default-metric <value>
The <value> indicates the metric and can be a value from 0 – 4294967295.