Cisco Nexus 3548 Command Reference Manual page 187

Chapter Unicast Routing Commands
Usage Guidelines Extended community values are configured as a 6-byte number. The first four bytes represent the
autonomous system number, and the last two bytes represent a user-defined network number. The BGP
generic specific community attribute is defined in
draft-ietf-idr-as4octet-extcomm-generic-subtype-00.txt.
BGP extended community exchange is not enabled by default. Use the send-extcommunity command
in BGP neighbor fix-family configuration mode to enable extended community attribute exchange
between BGP peers.
Once you configure a permit value to match a given set of extended communities, the extended
community list defaults to an implicit deny for all other extended community values.
Standard Extended Community Lists
Use standard extended community lists to configure specific extended community numbers. You can
configure a maximum of 16 extended communities in a standard extended community list.
Expanded Extended Community Lists
Use expanded extended community lists to filter communities using a regular expression. Use regular
expressions to configure patterns to match community attributes. The order for matching using the * or
+ character is the longest construct is first. Nested constructs are matched from the outside in.
Concatenated constructs are matched beginning at the left side. If a regular expression can match two
different parts of an input string, it matches the earliest part first.
Community List Processing
When you configure multiple values in the same extended community list statement, a logical AND
condition is created. All extended community values must match to satisfy the AND condition. When
you configure multiple values in separate community list statements, a logical OR condition is created.
The first list that matches a condition is processed.
This command requires the LAN Enterprise Services license.
Examples This example shows how to configure a standard generic specific extended community list that permits
routes from network 40 in autonomous system 1.65534 and from network 60 in autonomous system
1.65412:
switch# configure terminal
switch(config)# ip extcommunity-list standard test1 permit generic transitive 1.65534:40
switch(config)#
All community values must match in order for the list to be processed.
This example shows how to configure an expanded extended community list that permits advertisements
that contain a route target extended community attribute beginning with the pattern 100:.
switch# configure terminal
switch(config)# ip extcommunity-list expanded test2 permit 100:+
switch(config)#
Related Commands Command
feature bgp
match extcommunity
OL-27852-01
Description
Enables BGP.
Matches an extended community in a route map.
Cisco Nexus 3548 Switch NX-OS Unicast Routing Command Reference
ip extcommunity-list
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