Adding an AS_Path Filter to an AS_Path List

Scenarios

This section describes how to add an AS_Path filter to an AS_Path list. Each AS_Path list can have multiple AS_Path filters.

Notes and Constraints

• AS_Path filters change the path through which network traffic passes. If a route policy has already been associated with an enterprise router, evaluate the impact on services before adding an AS_Path filter to an AS_Path list.
• Each filter in an AS_Path list must have its unique sequence number.

Prerequisites

An AS_Path list is available. You can create one by referring to Creating an AS_Path List.

Procedure

1. Log in to the management console.
2. Click in the upper left corner and select the desired region and project.
3. Click Service List and choose Networking > Enterprise Router.

   The Enterprise Router homepage is displayed.

4. In the navigation pane on the left, choose Routing Control > AS_Path Lists.

   The AS_Path Lists page is displayed.

5. Click the name of the target AS_Path list.

   The AS_Path filters are displayed.

6. Click Add AS_Path Filter in the upper left corner of the filter list.

   The Add AS_Path Filter dialog box is displayed.

7. Configure the parameters based on Table 1.

   Table 1 Parameters for adding an AS_Path filter

   Parameter	Description	Example Value
   Sequence Number	Mandatory An AS_Path list consists of one or more AS_Path filters that are applied to filter routes based on their sequence numbers, in ascending order. A sequence number can be from 0 to 65535.	10
   Action	Mandatory Select Allow or Deny. If a route matches an AS_Path filter with Action set to Allow, the route is allowed. If the AS_Path filter has Action set to Deny, the route is denied.	Allow
   Regular Expression	A regular expression is a string that describes a characteristic and verifies whether another string conforms to this characteristic. An AS_Path filter defines an AS_Path regular expression to match AS_Path attributes of BGP routes for filtering BGP routes. For details, see AS_Path Regular Expressions.	65+

8. Click OK.

   In the AS_Path filter list, you can view the created AS_Path filter.

Follow-Up Operations

Deleting an AS_Path Filter from an AS_Path List: An AS_Path filter cannot be modified after being added. You can delete an AS_Path filter that you do not need and add another one.