Description: This key attribute allows the user to enter a regular expression to match the import Community Attribute of the received update message. The syntax of the regular expression is a subset of the RFC 2280. The basic syntax of a regular expression is a list of Community number seperated by a space which making up a Community attribute. The following characters has the special meaning: '[n1 ... n2]' - Matches any Community number that appeared in the set n1 ... n2. 'n1 - n2' - Matches any Community number between the range of n1 and n2. '()' - is supported to change the order of evaluation. 'n*' - Matches 0 or more occurrences of n, where n can be a set, range or Community number. 'n+' - Matches 1 or more occurrences of n, where n can be a set, range or Community number. 'n?' - Matches 0 or 1 occurrences of n, where n can be a set, range or number. The following logical operators are evaluated in decending order: 'NOT' - Given a regular expression x, NOT x matches the Community attribute that is not matched by x. 'AND' - Given two regular expressions x and y, x AND y matches the intersection of the Community attribute that are matched by x and those are matched by y. 'OR' - Given two regular expressions x and y, x OR y matches the union of the Community attribute that are matched by x and those are matched by y. For example: The Community path '1 2 3 4 5' would be match by any one of the following regular expression: 1, 5, 4 3, 2 3 - 4*, 1 [3 4 2]+, not (6 7 8 9 10) and 1 2 Empty regular expression implies a match on all Community path.