Dell PowerConnect B-RX Configuration Manual page 868

26
Filtering
A community is an optional attribute that identifies the route as a member of a user-defined class
of routes. Community names are arbitrary values made of two five-digit integers joined by a colon.
You determine what the name means when you create the community name as one of a route's
attributes. Each string in the community name can be a number from 0 – 65535.
This format allows you to easily classify community names. For example, a common convention
used in community naming is to configure the first string as the local AS and the second string as
the unique community within that AS. Using this convention, communities 1:10, 1:20, and 1:30
can be easily identified as member communities of AS 1.
The device provides the following methods for filtering on community information:
•
•
NOTE
The BigIron RX cannot actively support community filters and community list ACLs at the same time.
Use one method or the other but do not mix methods.
NOTE
Once you define a filter or ACL, the default action for communities that do not match a filter or ACL
is "deny". To change the default action to "permit", configure the last filter or ACL entry as "permit
any any".
Community filters or ACLs can be referred to by match statements in a route map.
Defining a community ACL
To configure community ACL 1, enter a command such as the following.
BigIron RX(config)# ip community-list 1 permit 123:2
This command configures a community ACL that permits routes that contain community 123:2.
NOTE
Refer to
community list as a match condition in a route map.
Syntax: ip community-list standard <string> [seq <seq-value>] deny | permit <community-num>
Syntax: ip community-list extended <string> [seq <seq-value>] deny | permit
The <string> parameter specifies the ACL name. (If you enter a number, the CLI interprets the
number as a text string.)
The standard or extended parameter specifies whether you are configuring a standard community
ACL or an extended one. A standard community ACL does not support regular expressions whereas
an extended one does. This is the only difference between standard and extended IP community
lists.
The seq <seq-value> parameter is optional and specifies the community list's sequence number.
You can configure up to 199 entries in a community list. If you do not specify a sequence number,
the software numbers them in increments of 5, beginning with number 5. The software interprets
the entries in a community list in numerical order, beginning with the lowest sequence number.
796
Community filters - refer to
Community list ACLs
"Matching based on community ACL"
<community-num> | <regular-expression>
"Defining a community filter"
on page 802 for information about how to use a
on page 751.
BigIron RX Series Configuration Guide
53-1001810-01