Dell Brocade DCX, Configuration Manual

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764 BigIron RX Series Configuration Guide
53-1001810-01
Originating the default route
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Originating the default route
By default, the device does not originate and advertise a default route using BGP4. A BGP4 default
route is the IP address 0.0.0.0 and the route prefix 0 or network mask 0.0.0.0. For example,
0.0.0.0/0 is a default route.
NOTE
The BigIron RX checks for the existence of an IGP route for 0.0.0.0/0 in the IP route table before
creating a local BGP route for 0.0.0.0/0.
To enable the router to originate and advertise a default BGP4 route, enter the following command.
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 798. 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.