Juniper JUNOSE, Configuration Manual

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Use to create a standard or a regular expression community list for BGP and
controls access to it.
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A route can belong to any number of communities, so a community list can have
many entries comprising many communities.
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You can specify one or more community values when you create a community
list. A clause in a route map that includes a list having more than one value only
matches a route having all of the values; that is, the multiple values are logical
ANDed.
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Example
host1(config)# ip community-list 1 permit 100:2 100:3 100:4
host1(config)# route-map marengo permit 10
host1(config-route-map)# match community 1
A route matches this community list only if it belongs to at least all three
communities in community list 1: Communities 100:2, 100:3, and 100:4.
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Use the no version to remove a single community list entry if permit or deny
and a path-expression are specified. Otherwise, the entire community list is
removed.
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See ip community-list.
The router supports the new BGP extended community attribute. This attribute
enables the definition of a new type of IP extended community and extended
community list unrelated to the community list that uses regular expressions. BGP
speakers can use the new extended community attribute to control routes similarly
to the way it uses the community attribute. The extended community attribute is
currently defined in the Internet draft, BGP Extended Communities
Attribute—draft-ietf-idr-bgp-ext-communities-07.txt (February 2004 expiration).
NOTE: IETF drafts are valid for only 6 months from the date of issuance. They must
be considered as works in progress. Please refer to the IETF Web site at
http://www.ietf.org for the latest drafts.
ip extcommunity-list
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Use to create an extended community list for BGP and control access to it.
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A route can belong to any number of communities, so an extended community
list can have many entries comprising many communities.
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You can specify one or more community values when you create an extended
community list. A clause in a route map that includes a list having more than
one value only matches a route having all of the values; that is, the multiple
values are logical ANDed.
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Example
host1(config)# ip extcommunity-list boston1 permit 100:2 100:3 100:4
host1(config)# route-map marengo permit 10
host1(config-route-map)# match extcommunity boston1
Configuring BGP Routing Policy
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Chapter 1: Configuring BGP Routing