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Example: Configuring MPLS-Based Layer 3 VPNs on EX Series Switches

You can implement an MPLS-based Layer 3 virtual private network (VPN) on EX8200 and EX4500 switches to interconnect sites for customers who want the service provider to handle all the Layer 3 routing functions. To support an MPLS-based Layer 3 VPN, you need to add components of the Layer 3 VPN to the configuration of the two provider edge (PE) switches. You do not need to change the configuration of the provider switches.

Note: The core interfaces and the loopback interfaces are configured in the same way for Layer 2 VPNs and Layer 3 VPNs.

This example shows how to configure an MPLS-based Layer 3 VPN spanning two corporate sites:

Requirements

This example uses the following software and hardware components:

• Junos OS Release 11.1 or later for EX Series switches
• Three EX8200 switches

Before you configure the Layer 3 VPN components, you must configure the basic components for an MPLS network:

• Configure two PE switches. See Configuring MPLS on Provider Edge Switches Using IP Over MPLS (CLI Procedure).
• Configure one or more provider switches. See Configuring MPLS on Provider Switches (CLI Procedure).

Note: A Layer 3 VPN requires that the PE switches be configured using IP over MPLS.

Overview and Topology

Layer 3 VPNs allow customers to leverage the service provider’s technical expertise to ensure efficient site-to-site routing. The customer’s customer edge (CE) switch uses a routing protocol such as BGP or OSPF to communicate with the service provider’s provider edge (PE) switch to carry IP prefixes across the network. MPLS-based Layer 3  VPNs use only IP over MPLS; other protocol packets are not supported. This example includes two PE switches, PE1 and PE2.

In the basic MPLS configuration of the PE switches using IP over MPLS, the PE switches were configured to use OSPF as the routing protocol between the MPLS switches and RSVP as the signaling protocol. Traffic engineering was enabled. A label-switched path (LSP) was configured.

Note: A static path is not configured in this example.

The following components must be added to the PE switches for an MPLS-based Layer 3 VPN:

• BGP group with family inet-vpn unicast
• Routing instance with instance type vrf

Figure 1 illustrates the topology of this MPLS-based Layer 3 VPN.

Figure 1: MPLS-Based Layer 3 VPN

Table 1 shows the settings of the customer edge interface on the local CE switch.

Table 2 shows the settings of the customer edge interface on the remote CE switch.

Table 3 shows the Layer 3 VPN components of the local PE switch.

Table 4 shows the Layer 3 VPN components of the remote PE switch.

Configuring the Local PE Switch

CLI Quick Configuration

To quickly configure the Layer 3 VPN components on the local PE switch, copy the following commands and paste them into the switch terminal window of PE1:

Step-by-Step Procedure

1. Configure BGP, specifying the loopback address as the local address and specifying family inet-vpn unicast:
   [edit protocols bgp]
user@switchPE1# set group ibgp local-address 21.21.21.21 family inet-vpn unicast
2. Configure the BGP group, specifying the group name and type:
   [edit protocols bgp]
user@switchPE1# set group ibgp type internal
3. Configure the BGP neighbor, specifying the loopback address of the remote PE switch as the neighbor’s address:
   [edit protocols bgp]
user@switchPE1# set group ibgp neighbor 22.22.22.22
4. Configure the routing instance, specifying the routing-instance name and using vrf as the instance type:
   [edit routing-instances]
user@switchPE1# set L3VPN-1 instance-type vrf
5. Configure a description for this routing instance:
   [edit routing-instances]
user@switchPE1# set L3VPN-1 description "BETWEEN PE1 AND PE2"
6. Configure the routing instance to use a route distinguisher:
   [edit routing-instances]
user@switchPE1# set L3VPN-1 route-distinguisher 21:21

   Note: Each routing instance that you configure on a PE switch must have a unique route distinguisher associated with it. VPN routing instances require a route distinguisher to allow BGP to distinguish between potentially identical network layer reachability information (NLRI) messages received from different VPNs. If you configure different VPN routing instances with the same route distinguisher, the commit fails.

7. Configure the VPN routing and forwarding (VRF) target of the routing instance:
   [edit routing-instances]
user@switchPE1# set L3VPN-1 vrf-target target:21:21

   Note: You can create more complex policies by explicitly configuring VRF import and export policies using the import and export options. See the Junos OS VPNs Configuration Guide.

8. Configure this routing instance with vrf-table-label, which maps the inner label of a packet to a specific VPN routing and forwarding (VRF) table and allows the examination of the encapsulated IP header:
   [edit routing-instances]
user@switchPE1# set L3VPN-1 vrf-table-label
9. Configure the router ID and autonomous system (AS):

   Note: We recommend that you explicitly configure the router identifier under the [edit routing-options] hierarchy level to avoid unpredictable behavior if the interface address on a loopback interface changes.

   [edit routing-options]
user@switchPE1# set router-id 21.21.21.21 autonomous-system 10

Results

Display the results of the configuration:

Configuring the Remote PE Switch

CLI Quick Configuration

To quickly configure the Layer 3 VPN components on the remote PE switch, copy the following commands and paste them into the switch terminal window of PE2:

Step-by-Step Procedure

1. Configure BGP, specifying the loopback address as the local address and specifying family inet-vpn unicast:
   [edit protocols bgp]
user@switchPE2# set group ibgp local-address 22.22.22.22 family inet-vpn unicast
2. Configure the BGP group, specifying the group name and type:
   [edit protocols bgp]
user@switchPE2# set group ibgp type internal
3. Configure the BGP neighbor, specifying the loopback address of the remote PE switch as the neighbor’s address:
   [edit protocols bgp]
user@switchPE2# set group ibgp neighbor 21.21.21.21
4. Configure the routing instance, specifying the routing-instance name and using vrf as the instance type:
   [edit routing-instances]
user@switchPE2# set L3VPN-1 instance-type vrf
5. Configure a description for this routing instance:
   [edit routing-instances]
user@switchPE1# set L3VPN-1 description "BETWEEN PE1 AND PE2"
6. Configure the routing instance to apply to the customer edge interface:
   [edit routing-instances]
user@switchPE2# set L3VPN-1 interface ge-11/0/14.0
7. Configure the routing instance to use a route distinguisher, using the format ip-address:number:
   [edit routing-instances]
user@switchPE2# set L3VPN-1 route-distinguisher 21:21
8. Configure the VPN routing and forwarding (VRF) target of the routing instance:
   [edit routing-instances]
user@switchPE2# set L3VPN-1 vrf-target target:21:21
9. Configure this routing instance with vrf-table-label, which maps the inner label of a packet to a specific VPN routing and forwarding (VRF) table and allows the examination of the encapsulated IP header.
   [edit routing-instances]
user@switchPE2# set L3VPN-1 vrf-tabel-label
10. Configure the router ID and autonomous system (AS):
    [edit routing-options]
user@switchPE2# set router-id 22.22.22.22 autonomous-system 10

Results

Display the results of the configuration:

Verification

To confirm that the MPLS-based Layer 3 VPN is working properly, perform these tasks:

• Verifying Peering and Adjacency
• Verifying That the Local CE Switch Can Ping the Local PE Switch
• Verifying That the Local PE Switch Can Ping the Local CE Switch

Verifying Peering and Adjacency

Purpose

Verify the peering and adjacency along the route from CE1 (the local CE switch or router) to CE2 (the remote CE switch or router), starting with checking the routing protocol adjacency on the local PE switch:

Note: Be sure to specify the name of the routing instance.

Action

Address    Interface   State ID         Pri Dead
51.51.0.14 ge-5/0/24.0 Full 21.21.21.21 128 38

Meaning

The Address field shows the IP address of the customer edge interface that connects CE1 to PE1. The Interface field shows the interface name of the customer edge interface that connects PE1 to CE1. For our purposes, the State field is the most important. It shows a status of Full, indicating that neighboring routing devices are fully adjacent. These adjacencies appear in router-link and network-link advertisements. (The field Pri indicates the priority of the neighbor to become the designated router. The field Dead indicates the number of seconds until the neighbor becomes unreachable.)

Verifying That the Local CE Switch Can Ping the Local PE Switch

Purpose

Verify that the local CE switch can ping the local PE switch:

Action

PING 51.51.0.1 (51.51.0.1): 56 data bytes
64 bytes from 51.51.0.1: icmp_seq=0 ttl=64 time=3.461 ms
64 bytes from 51.51.0.1: icmp_seq=1 ttl=64 time=3.543 ms

Meaning

This command specified the IP address of the customer edge interface on PE1. The results indicate that CE1 is receiving packets from PE1.

Verifying That the Local PE Switch Can Ping the Local CE Switch

Purpose

Verify that the local PE switch can ping the local CE switch:

Action

PING 51.51.0.14 (51.51.0.14): 56 data bytes
64 bytes from 51.51.0.14: icmp_seq=0 ttl=64 time=3.842 ms
64 bytes from 51.51.0.14: icmp_seq=1 ttl=64 time=3.736 ms

Meaning

The results indicate a successful connection.