Help us improve your experience.

Let us know what you think.

Do you have time for a two-minute survey?

 
 

Example: Configuring a Routing Policy to Prepend the AS Path

This example shows how to configure a routing policy to prepend the AS path.

Requirements

Before you begin, make sure your router interfaces and protocols are correctly configured.

Overview

In this example, you create a routing policy called prependpolicy1 and a term called prependterm1. The routing policy prepends the AS numbers 1 1 1 1 to routes that are greater than or equal to 172.16.0.0/12, 192.168.0.0/16, and 10.0.0.0/8. The policy is applied as an import policy to all BGP routes and is evaluated when routes are imported to the routing table.

Topology

Configuration

Procedure

CLI Quick Configuration

To quickly configure this example, copy the following commands, paste them into a text file, remove any line breaks, change any details necessary to match your network configuration, and then copy and paste the commands into the CLI at the [edit] hierarchy level.

Step-by-Step Procedure

The following example requires you to navigate various levels in the configuration hierarchy. For instructions on how to do that, see Using the CLI Editor in Configuration Mode in the Junos OS CLI User Guide.

To create a routing policy that prepends AS numbers to multiple routes:

  1. Create the routing policy.

  2. Create the routing term.

  3. Specify the routes to prepend with AS numbers.

  4. Specify the AS numbers to prepend.

    Note:

    If you enter multiple numbers, you must separate each number with a space. Enclose the numbers in double quotation marks.

  5. Apply the policy as an import policy for all BGP routes.

    Note:

    You can refer to the same routing policy one or more times in the same or different import statement.

Results

Confirm your configuration by entering the show policy-options and show protocols bgp commands from configuration mode. If the output does not display the intended configuration, repeat the configuration instructions in this example to correct it.

If you are done configuring the device, enter commit from configuration mode.

Verification

To confirm that the configuration is working properly, perform these tasks:

Verifying the AS Numbers to Prepend

Purpose

Verify that the policy and term are configured on the device and that the appropriate routes are specified to prepend with AS numbers.

Action

From operational mode, enter the show policy-options command.

Verifying the Routing Policy

Purpose

Verify that the routing policy is applied to the routing protocol.

Action

From operational mode, enter the show protocols bgp command.