Dell Force10 S4810P Configuration Manual page 215

Use these commands in the following sequence, starting in the CONFIGURATION mode to configure an
AS-PATH ACL to filter a specific AS_PATH value.
Step Command Syntax
1 ip as-path access-list
as-path-name
2
{ deny | permit } filter
parameter
3 exit
4
router bgp as-number
5 {
neighbor
ip-address
peer-group-name
filter-list as-path-name
{ | }
in out
Regular Expressions as filters
Regular expressions are used to filter AS paths or community lists. A regular expression is a special
character used to define a pattern that is then compared with an input string.
For an AS-path access list as shown in the commands above, if the AS path matches the regular expression
in the access list, then the route matches the access list.
Figure 9-27 applies access list Eagle to routes inbound from BGP peer 10.5.5.2. Access list Eagle uses a
regular expression to deny routes originating in AS 32.
Command Mode
CONFIGURATION
CONFIG-AS-PATH
AS-PATH ACL
CONFIGURATION
|
CONFIG-ROUTER-B
GP
}
Purpose
Assign a name to a AS-PATH ACL and enter AS-PATH
ACL mode.
Enter the parameter to match BGP AS-PATH for
filtering. This is the filter that will be used to match the
AS-path. The entries can be any format, letters,
numbers, or regular expressions.
This command can be entered multiple times if multiple
filters are desired.
See Table 9-4 for accepted expressions.
Return to CONFIGURATION mode
Enter ROUTER BGP mode.
Use a configured AS-PATH ACL for route filtering and
manipulation.
If you assign an non-existent or empty AS-PATH ACL,
the software allows all routes.
Border Gateway Protocol | 215