Help us improve your experience.

Let us know what you think.

Do you have time for a two-minute survey?

 
 

Example: Configuring an Export Policy for BGP Route Target Filtering for VPNs

This example shows how to configure an export routing policy for BGP route target filtering (also known as route target constrain, or RTC).

Requirements

This example uses the following hardware and software components:

  • Four Juniper Networks devices that support BGP route target filtering.

  • Junos OS Release 12.2 or later on one or more devices configured for proxy BGP route filtering. In this example, you explicitly configure proxy BGP route filtering on the route reflectors.

Before configuring an export policy for BGP route target filtering, make sure that you are familiar with and understand the following concepts:

Overview

BGP route target filtering allows you to reduce network resource consumption by distributing route target membership (RT membership) advertisements throughout the network. BGP uses the RT membership information to send VPN routes only to the devices that need them in the network. Similar to other types of BGP reachability, you can apply a routing policy to route target filtering routes to influence the network. When route target filtering is configured, restricting the flow of route target filtering routes also restricts the VPN routes that might be attracted by this RT membership. Configuring this policy involves:

  • Creating a filter that defines the list of route target prefixes.

  • Creating a policy to select a subset of the route target filters to use for BGP route target filtering.

To define the list of route target prefixes:

  • You configure the rtf-prefix-list statement at the [edit policy-options] hierarchy level to specify the name of the route target prefix list and one or more route target prefixes to use. This configuration allows you to specify the incoming route target filtering routes that the device will use and then distribute them throughout the network.

To configure the routing policy and apply the route target prefix list to that policy, you can specify the following policy options:

  • family route-target—(Optional) The route-target family match condition specifies matching BGP route target filtering routes. You define this criteria in the from statement. This example shows how to create an export policy using the family route-target match condition.

  • protocol route-target—(Optional) The route-target protocol match condition defines the criteria that an incoming route must match. You define this criteria in the from statement. This statement is primarily useful for restricting the policy to locally generated route target filtering routes.

    Note:

    When you use the show route table bgp.rtarget.0 command to view proxy BGP route target filtering routes, you will see the BGP protocol for received routes and the route target protocol routes for local route target filtering routes.

  • rtf-prefix-list name—The rtf-prefix-list statement applies the list of route target prefixes that you already configured to the policy. You define this criteria in the from statement.

Topology Diagram

Figure 1 shows the topology used in this example.

Figure 1: BGP Route Target Filtering Export Policy TopologyBGP Route Target Filtering Export Policy Topology

In this example, BGP route target filtering is configured on the route reflectors (Device RR1 and Device RR2) and provider edge (PE) Device PE2. The other PE, Device PE1, does not support BGP route target filtering. Proxy BGP route target filtering is also configured on the peering sessions between the route reflectors and Device PE1 to minimize the number of VPN route updates processed by Device PE1. Device PE2 has four VPNs configured (vpn1, vpn2, vpn3, and vpn4), and Device PE1 has two VPNs configured (vpn1 and vpn2). In the sample topology, all devices participate in autonomous system (AS) 203, OSPF is the configured interior gateway protocol (IGP), and LDP is the signaling protocol used by the VPNs. In this example, we use static routes in the VPN routing and forwarding (VRF) instances to generate VPN routes. This is done in place of using a PE to customer edge (CE) protocol such as OSPF or BGP.

In this example, you further control the routes being advertised from Device PE2 to Device PE1 by configuring an export policy on Device PE2 to prevent vpn3 routes from being advertised to Device RR1. You create a policy that specifies the family route-target match condition, defines the list of route target prefixes, and applies the list of route target prefixes by defining the rtf-prefix-list criteria.

Configuration

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.

Device PE1

Device RR1

Device RR2

Device PE2

Configuring Device PE1

Step-by-Step Procedure

The following example requires you to navigate various levels in the configuration hierarchy. For information about navigating the CLI, see Using the CLI Editor in Configuration Mode.

To configure Device PE1:

  1. Configure the interfaces.

  2. Configure the route distinguisher and the AS number.

  3. Configure LDP as the signaling protocol used by the VPN.

  4. Configure BGP.

  5. Configure OSPF.

  6. Configure the VPN routing instances.

  7. If you are done configuring the device, commit the configuration.

Results

From configuration mode, confirm your configuration by entering the show interfaces, show protocols, show routing-options, and show routing-instances commands. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

Configuring Device RR1

Step-by-Step Procedure

The following example requires you to navigate various levels in the configuration hierarchy. For information about navigating the CLI, see Using the CLI Editor in Configuration Mode.

To configure Device RR1:

  1. Configure the interfaces.

  2. Configure the route distinguisher and the AS number.

  3. Configure LDP as the signaling protocol used by the VPN.

  4. Configure BGP.

  5. Configure BGP route target filtering on the peering session with Device PE2.

  6. Configure proxy BGP route target filtering on the peering session with Device PE1.

  7. Configure OSPF.

  8. If you are done configuring the device, commit the configuration.

Results

From configuration mode, confirm your configuration by entering the show interfaces, show protocols, and show routing-options commands. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

Configuring Device RR2

Step-by-Step Procedure

The following example requires you to navigate various levels in the configuration hierarchy. For information about navigating the CLI, see Using the CLI Editor in Configuration Mode.

To configure Device RR2:

  1. Configure the interfaces.

  2. Configure the route distinguisher and the AS number.

  3. Configure LDP as the signaling protocol used by the VPN.

  4. Configure BGP.

  5. Configure BGP route target filtering on the peering session with Device PE2.

  6. Configure proxy BGP route target filtering on the peering session with Device PE1.

  7. Configure OSPF.

  8. If you are done configuring the device, commit the configuration.

Results

From configuration mode, confirm your configuration by entering the show interfaces, show protocols, and show routing-options commands. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

Configuring Device PE2

Step-by-Step Procedure

The following example requires you to navigate various levels in the configuration hierarchy. For information about navigating the CLI, see Using the CLI Editor in Configuration Mode.

To configure Device PE2:

  1. Configure the interfaces.

  2. Configure the route distinguisher and the AS number.

  3. Configure LDP as the signaling protocol used by the VPN.

  4. Configure BGP.

  5. Configure OSPF.

  6. Configure the VPN routing instances.

  7. Configure and apply the export routing policy.

  8. If you are done configuring the device, commit the configuration.

Results

From configuration mode, confirm your configuration by entering the show interfaces, show protocols, show policy-options, show routing-options, and show routing-instances commands. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

Verification

Confirm that the configuration is working properly.

Verifying the Route Target Filtering Routes in the bgp.rtarget.0 Routing Table for Device RR1

Purpose

Verify that the route prefix for vpn3 is not in Device RR1’s bgp.rtarget.0 table. Since an export policy on Device PE2 was applied to prevent the advertisement of vpn3 routes to Device RR1, Device RR1 should not receive those advertisements.

Action

From operational mode, enter the show route advertising-protocol bgp 10.255.165.220 table bgp.rtarget.0 command.

Meaning

The bgp.rtartget.0 table does not display 203:203:103/96, which is the route prefix for vpn3. That means the export policy was applied correctly.

Verifying the Route Target Filtering Routes in the bgp.rtarget.0 Routing Table for Device RR2

Purpose

Verify that the route prefix for vpn3 is in Device RR2’s bgp.rtarget.0 table. Since an export policy was not applied on Device PE2 to prevent the advertisement of vpn3 routes to Device RR2, Device RR2 should receive advertisements from all of the VPNs.

Action

From operational mode, enter the show route advertising-protocol bgp 10.255.165.28 table bgp.rtarget.0 command.

Meaning

The bgp.rtartget.0 table displays the route prefixes for all of the VPNs.