Advertising a Default Route
You can configure BGP to send a default route to indicate that the speaker accepts routes
for any VPNs associated with any route target. For example, this might be desirable for
a route reflector advertising to one of its PE router clients, or when a VPN provider is
migrating the network to route-target filtering but one or more PEs in the provider's
network do not support this feature.
When you configure the default route, the RT-MEM-NLRI attribute contains 0:0:0/0 as
the Default-RT-MEM-NLRI. This 4-byte prefix contains only the local (origin) AS number
field, set to zero.
By default, BGP does not generate or advertise the Default-RT-MEM-NLRI route. You
can use the default-information originate command to generate the
Default-RT-MEM-NLRI route and send it to all peers. You can use the neighbor
default-originate command generate the route and send it to a particular peer group.
The configuration must be the same for all members of the peer group.
A BGP speaker sends the Default-RT-MEM-NLRI route only to the peers with which it
has negotiated the route-target filtering capability. Any other peers are considered to be
unaware of this capability and have no use for that route.
default-information originate
• Use in the route-target address family to cause a BGP speaker (the local router) to
send the Default-RT-MEM-NLRI route (0:0:0/0) to all peers for use as a default route.
• Use the route-map keyword to specify outbound route maps to apply to the default
route. The route map can modify the attributes of the default route.
• This command takes effect immediately. However, if the contents of the route map
specified with this command change, the new route map may or may not take effect
immediately. If the disable-dynamic-redistribute command has been configured, you
must issue the clear ip bgp redistribution command to apply the changed route map.
• Outbound policy configured for the neighbor (using the neighbor route-map out
command) is applied to default routes that are advertised because of the
default-information originate command.
• Policy specified by a route map with the default-information originate command is
applied at the same time as the policy for redistributed routes, before any outbound
policy for peers.
• Example
host1(config-router)#router address-family route-target
host1(config-router-af)#default-information originate
• Use the no version to restore the default, preventing the redistribution of default routes.
• See default-information originate.
neighbor default-originate
Copyright © 2010, Juniper Networks, Inc.418
JunosE 11.2.x BGP and MPLS Configuration Guide
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