Foundry Networks FESX User Manual

Configuring BGP4
December 2005 © Foundry Networks, Inc. 21 - 25
To configure a route map, and use it to set or change route attributes for a network you define for BGP4 to
advertise, enter commands such as the following:
FESX424 Router(config)# route-map set_net permit 1
FESX424 Router(config-routemap set_net)# set community no-export
FESX424 Router(config-routemap set_net)# exit
FESX424 Router(config)# router bgp
FESX424 Router(config-bgp-router)# network 100.100.1.0/24 route-map set_net
The first two commands in this example create a route map named “set_net” that sets the community attribute for
routes that use the route map to “NO_EXPORT”. The next two commands change the CLI to the BGP4
configuration level. The last command configures a network for advertising from BGP4, and associates the
“set_net” route map with the network. When BGP4 originates the 100.100.1.0/24 network, BGP4 also sets the
community attribute for the network to “NO_EXPORT”.
Syntax: network <ip-addr> <ip-mask> [route-map <map-name>] | [weight <num>] | [backdoor]
The route-map <map-name> parameter specifies the name of the route map you want to use to set or change
BGP4 attributes for the network you are advertising. The route map must already be configured.
For information about the other parameters, see “Defining Route Maps” on page 21-48.
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. See “Defining Route Maps” on page 21-
48. See “How BGP4 Selects a Path for a Route” on page 21-4 for information about the BGP4 algorithm.
To change the default local preference to 200, enter the following command:
FESX424 Router(config-bgp-router)# default-local-preference 200
Syntax: default-local-preference <num>
The <num> parameter indicates the preference and can be a value from 0 – 4294967295.
Using the IP Default Route as a Valid Next Hop for a BGP4 Route
By default, the Layer 3 Switch does not use a default route to resolve a BGP4 next-hop route. If the IP route
lookup for the BGP4 next hop does not result in a valid IGP route (including static or direct routes), the BGP4 next
hop is considered to be unreachable and the BGP4 route is not used.
In some cases, such as when the Layer 3 Switch is acting as an edge router, you might want to allow the device to
use the default route as a valid next hop. To do so, enter the following command at the BGP4 configuration level of
the CLI:
FESX424 Router(config-bgp-router)# next-hop-enable-default
Syntax: [no] next-hop-enable-default

Foundry Networks FESX Specifications

General

Brand	Foundry Networks
Model	FESX
Category	Switch
Language	English