Configure Packet Forwarding for Layer 3 VPNs

You can configure the router to support packet forwarding for Internet Protocol version 4 (IPv4) traffic in Layer 2 and Layer 3 VPNs. Packet forwarding is handled in one of the following ways, depending on the type of helper service configured:

• BOOTP service—Clients send Bootstrap Protocol (BOOTP) requests through the router configured with BOOTP service to a server in the specified routing instance. The server recognizes the client address and sends a response back to the router configured with BOOTP service. This router forwards the reply to the correct client address in the specified routing instance.
• Other services—Clients send requests through the router configured with the service to a server in the specified routing instance. The server recognizes the client address and sends a response to the correct client address in the specified routing instance.

To enable packet forwarding for VPNs, configure the helpers statement:

helpers {

    service {

        description description-of-service;

        server {

            address address {

                routing-instance routing-instance-names;

            }

        }

        interface interface-name {

            description description-of-interface;

            no-listen;

        server {

            address address {

                routing-instance routing-instance-names;

            }

        }

    }

You can configure this statement at the following hierarchy levels:

• [edit logical-routers logical-router-name forwarding-options]
• [edit forwarding-options]
  
  

  You can enable packet forwarding for multiple VPNs. However, the client and server must be within the same VPN. Any Juniper Networks routers with packet forwarding enabled along the path between the client and server must also reside within the same VPN.

  
  

The address and routing instance together constitute a unique server. This has implications for routers configured with BOOTP service, which can accept multiple servers.

For example, a BOOTP service can be configured as follows:

server address 1.2.3.4 routing-instance [instance-A instance-B];

You can configure this statement at the following hierarchy levels:

• [edit logical-routers logical-router-name forwarding-options helpers bootp]
• [edit forwarding-options helpers bootp]

Though the addresses are identical, the routing instances are different. A packet coming in for BOOTP service on instance-A is forwarded to 1.2.3.4 in the instance-A routing instance, while a packet coming in on instance-B is forwarded in the instance-B routing instance. Other services can only accept a single server, so this configuration does not apply in those cases.

For more information about the statements configured at the [edit forwarding-options] hierarchy level, see the JUNOS Internet Software Configuration Guide: Policy Framework.