Brocade Communications Systems ICX 7250 series, Руководство по настройке

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NOTE
Once you define a filter or ACL, the default action for updates that do not match a filter is deny . To change the default action to
permit , configure the last filter or ACL as permit any any .
AS-path filters or AS-path ACLs can be referred to by the filter list number of a BGP4 neighbor as well as by match clauses in a route
map.
Defining an AS-path ACL
To configure an AS-path list that uses "acl 1", enter a command such as the following.
device(config)# ip as-path access-list acl1 permit 100
device(config)# router bgp
device(config-bgp-router)# neighbor 10.10.10.1 filter-list acl1 in
Syntax: [no] ip as-path access-list string [ seq s eq-value ] deny | permit regular-expression
The ip as-path command configures an AS-path ACL that permits routes containing AS number 100 in their AS paths. The neighbor
command then applies the AS-path ACL to advertisements and updates received from neighbor 10.10.10.1. In this example, the only
routes the device permits from neighbor 10.10.10.1 are those whose AS-paths contain AS-path number 100.
The string parameter specifies the ACL name. (If you enter a number, the CLI interprets the number as a text string.)
The seq seq-value parameter is optional and specifies the sequence number for the AS-path list. If you do not specify a sequence
number, the software numbers in increments of 5, beginning with number 5. The software interprets the entries in an AS-path list in
numerical order, beginning with the lowest sequence number.
The deny and permit parameters specify the action the software takes if the AS-path list for a route matches a match clause in this ACL.
To configure the AS-path match clauses in a route map, use the match as-path command.
The regular-expression parameter specifies the AS path information you want to permit or deny to routes that match any of the match
clauses within the ACL. You can enter a specific AS number or use a regular expression.
The neighbor command uses the filter-list parameter to apply the AS-path ACL to the neighbor.
Using regular expressions
Use a regular expression for the as-path parameter to specify a single character or multiple characters as a filter pattern. If the AS-path
matches the pattern specified in the regular expression, the filter evaluation is true; otherwise, the evaluation is false.
You can also include special characters that influence the way the software matches the AS-path against the filter value.
To filter on a specific single-character value, enter the character for the as-path parameter. For example, to filter on AS-paths that contain
the letter "z", enter the following command:
device(config-bgp-router)# ip as-path access-list acl1 permit z
To filter on a string of multiple characters, enter the characters in brackets. For example, to filter on AS-paths that contain "x", "y", or "z",
enter the following command.
device(config-bgp-router)# ip as-path access-list acl1 permit [xyz]
BGP4 Special characters
When you enter a single-character expression or a list of characters, you also can use the special characters listed in "Using regular
expressions." The description for each character includes an example. Some special characters must be placed in front of the characters
they control and others must be placed after the characters they control. The examples show where to place the special character.
Filtering
Brocade FastIron Layer 3 Routing Configuration Guide
324 53-1003903-04