Juniper JUNOSE 11.2.X BGP AND MPLS, Configuration Manual

Page: 100 / 742

•
VPNv4 unicast
• VPNv6 unicast
NOTE: For VPNv4 unicast and VPNv6 unicast address families, we recommend that
you include a match extcommunity clause to match a route with a specific route target.
However, conditional advertisement in these address families can sometimes result in
unintended behaviors: advertisement of or based on an incorrect VPN route or a non-VPN
route.
BGP conditional advertisement is not supported in the following address families:
• L2VPN
• Route-target
•
VPLS
•
VPWS
Use the exist-map keyword when you want a route advertised only when another route
is present. The determining route must match the specified route map. If the route map
you specify with the
exist-map keyword references multiple routes, only one of those
routes needs to be in the routing table to trigger the conditional advertisement.
Use the non-exist-map keyword when you want a route advertised only when another
route is absent. The determining route must match the specified route map. If the route
map you specify with the
non-exist-map keyword references multiple routes, all of those
routes must be absent to trigger the conditional advertisement.
You can optionally specify a sequence number for the advertise route map that matches
the determining route. The sequence number specifies the order in which the advertise
route maps are processed. It indicates the position the specified advertise route map has
in the list of all advertise route maps that are configured for a particular neighbor within
the same address family.
If you do not specify a sequence number, the position of the advertise route map is
considered to be the sum of the current largest sequence number plus five. An advertise
route map with a lower sequence number has a higher priority and is processed before
one with a higher sequence number.
If the route matches more than one advertise route map, only the first matching advertise
route map, based on the sequence, controls the advertisement of a BGP route.
You can configure a maximum of 50 advertise maps for a given peer or peer group in an
address family. However, the name and sequence number for the advertise route map
must be unique for each entry. BGP applies any policy specified by the advertise map to
the conditionally advertised routes before outbound policy specified for the neighbor is
applied.
The route maps referenced by the neighbor advertise-map command must include a
match ip-address clause. You can also include additional match clauses. All match
Copyright © 2010, Juniper Networks, Inc. 64
JunosE 11.2.x BGP and MPLS Configuration Guide