Community Lists; Figure 5: Community Lists; Table 4: Action Based On Well-Known Community Membership - Juniper JUNOSE 11.0.X IP SERVICES Configuration Manual

JUNOSe 11.0.x IP Services Configuration Guide
match-set summary prefix-tree

Community Lists

A community is a logical group of prefixes that share some common attribute.
Community members can reside on different networks and in different autonomous
systems. BGP enables you to define the community to which a prefix belongs. A
prefix can belong to more than one community. The community attribute lists the
communities to which a prefix belongs.
You can use communities to simplify routing policies by configuring the routing
information that a BGP device can accept, prefer, or distribute to other neighbors
according to community membership. When a route is learned, advertised, or
redistributed, a BGP device can set, append, or modify the community of a route.
When routes are aggregated, the resulting BGP update contains a community attribute
that contains all communities from all of the aggregated routes (if the aggregate is
an AS-set aggregate).
Several well-known communities are predefined. Table 4 on page 38 describes how
a BGP device handles a route based on the setting of its community attribute.

Table 4: Action Based on Well-Known Community Membership

38
Community Lists
Use with the prefix-tree keyword to match routes that have a next-hop router
address passed by the specified prefix tree.
Example
host1(config-route-map)#match ip next-hop prefix-tree xyz
Use the no version to delete the match clause from a route map or a specified
value from the match clause.
See match ip next-hop.
Use to specify the prefix tree that summarizes routes for a particular route map.
Use the ip prefix-tree command to set the conditions of the prefix tree, including
which routes to summarize and how many bits of the network address to
preserve.
Example
host1(config-route-map)#match-set summary prefix-tree dog3
Use the no version to disable use of the prefix tree by the route map.
See match-set summary prefix-tree.
Well-Known Community
no-export
no-advertise
BGP Device Action
Does not advertise the route beyond the BGP confederation
boundary
Does not advertise the route to any peers, IBGP, or EBGP