Juniper JUNOSE, Configuration Manual

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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
■
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 a peer group 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.
■
If you specify a BGP peer group by using the peerGroupName argument, all the
members of the peer group inherit the characteristic configured with this
Constraining Route Distribution with Route-Target Filtering
■ 409
Chapter 5: Configuring BGP-MPLS Applications