Dell BigIron RX Series, Руководство по настройке

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782 BigIron RX Series Configuration Guide
53-1002253-01
Using the IP default route as a valid next hop for a BGP4 route
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The <ip-addr> is the network number and the <ip-mask> specifies the network mask.
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; otherwise, the default action is to deny redistribution.
The weight <num> parameter specifies a weight to be added to routes to this network.
The backdoor parameter changes the administrative distance of the route to this network from the
EBGP administrative distance (20 by default) to the Local BGP weight (200 by default), thus tagging
the route as a backdoor route. Use this parameter when you want the router to prefer IGP routes
such as RIP or OSPF routes over the EBGP route for the network.
Specifying a route map name when configuring BGP4 network information
You can specify a route map as one of the parameters when you configure a BGP4 network to be
advertised. The device can use the route map to set or change BGP4 attributes when creating a
local BGP4 route.
NOTE
You must configure the route map before you can specify the route map name in a BGP4 network
configuration; otherwise, the route is not imported into BGP.
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.
BigIron RX(config)# route-map set_net permit 1
BigIron RX(config-routemap set_net)# set community no-export
BigIron RX(config-routemap set_net)# exit
BigIron RX(config)# router bgp
BigIron RX(config-bgp)# 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, refer to “ “Defining route maps” on page 801.
Using the IP default route as a valid next hop for a BGP4 route
By default, the BigIron RX 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 device 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.