1038 PowerConnect B-Series FCX Configuration Guide53-1002266-01Filtering30If you want to filter for a special character instead of using the special character, enter “\”(backslash) in front of the character. For example, to filter on AS-path strings containing anasterisk, enter the asterisk portion of the regular expression as “\*”.PowerConnect(config-bgp-router)#as-path-filter 2 deny \*To use the backslash as a string character, enter two slashes. For example, to filter on AS-pathstrings containing a backslash, enter the backslash portion of the regular expression as “\\”.PowerConnect(config-bgp-router)#as-path-filter 2 deny \\Filtering communitiesYou can filter routes received from BGP4 neighbors based on community names. Use either of thefollowing methods to do so.A community is an optional attribute that identifies the route as a member of a user-defined classof 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 routeattributes. Each string in the community name can be a number from 0 through 65535.This format allows you to easily classify community names. For example, a common conventionused in community naming is to configure the first string as the local AS and the second string asthe unique community within that AS. Using this convention, communities 1:10, 1:20, and 1:30can be easily identified as member communities of AS 1.The Layer 3 Switch provides the following methods for filtering on community information:• Community filters• Community list ACLs[ ] Square brackets enclose a range of single-character patterns. For example, the followingregular expression matches on an AS-path that contains “1”, “2”, “3”, “4”, or “5”:[1-5 ]You can use the following expression symbols within the brackets. These symbols are allowedonly inside the brackets:• ^ – The caret matches on any characters except the ones in the brackets. For example,the following regular expression matches on an AS-path that does not contain “1”, “2”,“3”, “4”, or “5”:[^1-5]• - The hyphen separates the beginning and ending of a range of characters. A matchoccurs if any of the characters within the range is present. See the example above.| A vertical bar (sometimes called a pipe or a “logical or”) separates two alternative values orsets of values. The AS-path can match one or the other value. For example, the followingregular expression matches on an AS-path that contains either “abc” or “defg”:(abc)|(defg)NOTE: The parentheses group multiple characters to be treated as one value. See thefollowing row for more information about parentheses.( ) Parentheses allow you to create complex expressions. For example, the following complexexpression matches on “abc”, “abcabc”, or “abcabcabcdefg”, but not on “abcdefgdefg”:((abc)+)|((defg)?)TABLE 182 BGP4 special characters for regular expressions (Continued)Character Operation
