# Configuring S-VLAN Tunnels for Layer 2 Services over MPLS

When you configure Ethernet layer 2 services over MPLS, you can create a special type of S-VLAN called an S-VLAN tunnel that uses a single interface to tunnel traffic from multiple VLANs across an MPLS network. The S-VLAN tunnel enables multiple VLANs, each configured with a unique VLAN ID tag, to share a common S-VLAN ID tag when they traverse an MPLS network.

## Advantages

Using S-VLAN tunnels provides an easier and faster way to configure Ethernet layer 2 services over MPLS than using standard S-VLANs. For example, consider the network configuration shown in Figure 19.

Figure 19: S-VLAN Tunnels for Ethernet Layer 2 Services over MPLS

In this example, traffic from three VLAN subinterfaces must traverse the MPLS network. To accomplish this using standard S-VLANs, you issue the following commands to configure three separate S-VLANs with the same S-VLAN ID value and different VLAN IDs, as follows:

host1(config-if)#svlan id 33 10 host1(config-if)#svlan id 33 20 host1(config-if)#svlan id 33 30

By contrast, using an S-VLAN tunnel achieves the same result, but requires you to issue only a single svlan id command with the keyword any in place of the VLAN ID value. For example, the following command creates a single interface that tunnels traffic from VLANs configured with an S-VLAN ID of 33 and any VLAN ID to the same destination across the MPLS network. In effect, this command tunnels traffic from all three VLANs shown in Figure 19.

host1(config-if)#svlan id 33 any

## Interface Stacking

When you configure Ethernet layer 2 services over MPLS using S-VLAN tunnels, the only interface that you can stack over an S-VLAN tunnel is an MPLS tunnel, which you configure using the MPLS tunneling command (mpls-relay or route interface) that is appropriate for your configuration. Attempting to configure any other interface type—such as IP, MPLS (nontunnel), or PPPoE—over the S-VLAN tunnel causes the router to generate an error and reject the configuration as invalid.

For details about configuring MPLS and layer 2 services over MPLS, see:

- Chapter Configuring MPLS in JunosE BGP and MPLS Configuration Guide
- Chapter Configuring Layer 2 Services over MPLS in JunosE BGP and MPLS Configuration Guide

## Configuration Example

This section uses the sample network topology shown in Figure 19 to illustrate the steps for configuring S-VLAN tunnels for Ethernet layer 2 services over MPLS.

To configure S-VLAN tunnels for Ethernet layer 2 services over MPLS:

1. Specify a Fast Ethernet, Gigabit Ethernet, or 10-Gigabit Ethernet port.
   host1(config)#interface fastEthernet 4/0
2. Specify VLAN as the encapsulation method to create the VLAN major interface.
   host1(config-if)#encapsulation vlan
3. Create a VLAN subinterface.
   host1(config-if)#interface fastEthernet 8/1.1
4. Create the S-VLAN tunnel. This interface tunnels traffic from VLANs configured with an S-VLAN ID of 33 and any VLAN ID to the same destination across the MPLS network.
   host1(config-if)#svlan id 33 any
5. Assign an S-VLAN Ethertype.
   host1(config-if)#svlan ethertype 8100
6. Create the MPLS tunnel interface using the appropriate MPLS tunneling command for your configuration. For example:
   host1(config-if)#route interface tunnel mpls:tunnel3 45

   For complete instructions on configuring the MPLS tunnel, see chapter Configuring Layer 2 Services over MPLS in JunosE BGP and MPLS Configuration Guide.

7. Repeat Steps 1 through 6 using unique values to configure the S-VLAN tunnel and MPLS tunnel interfaces on the remote E Series router. For example:
   host2(config)#interface fastEthernet 3/1 host2(config-if)#encapsulation vlan host2(config-if)#interface fastEthernet 3/1.1 host2(config-if)#svlan id 83 any host2(config-if)#svlan ethertype 88a8 host2(config-if)#route interface tunnel mpls:tunnel2 45

encapsulation vlan

- Use to configure VLAN as the encapsulation method for the interface.
- Use the no version to disable VLAN on an interface.
- See encapsulation vlan.

interface fastEthernet

- Use to select a Fast Ethernet interface on a line module.
- Example
  host1(config)#interface fastEthernet 3/1
- Use the no version to remove the interface or subinterface. You must issue the no version from the highest level down; you cannot remove an interface or subinterface if the one above it still exists.
- See interface fastEthernet.

route interface

- Use to route layer 2 traffic on a specific tunnel interface.
- Use the no version to negate this command.

  | Note: For details on the use of this command, see chapter Configuring Layer 2 Services over MPLS in JunosE BGP and MPLS Configuration Guide.

- See route interface.

svlan ethertype

- Use to assign an Ethertype value for the S-VLAN tunnel interface.
- Choose one of the following Ethertype values:
  - 8100—Specifies Ethertype value 0x8100, as defined in IEEE Standard 802.1q
  - 88a8—Specifies Ethertype value 0x88a8, as defined in draft IEEE Standard 802.1ad
  - 9100—Specifies Ethertype value 0x9100, which is the default
- Use an Ethertype value that matches the Ethertype value set on the customer premises equipment (CPE) to which your router connects.
- Example
  host1(config-if)#svlan ethertype 8100
- Use the no version to restore the default value, 9100.
- See svlan ethertype.

svlan id

- Use to create an S-VLAN tunnel interface for configuring Ethernet layer 2 services over MPLS.
- Assign an S-VLAN ID value in the range 0–4095 that is unique within the Ethernet interface.
- Use the any keyword to tunnel traffic from VLANs configured with the specified S-VLAN ID and any VLAN ID to the same destination across an MPLS network.
- Issue the svlan id command with the any keyword before you configure the upper binding, which must be an MPLS tunnel interface. Attempting to configure any other interface type over the S-VLAN tunnel causes an error.
- Example
  host1(config-if)#svlan id 1000 any
- There is no no version.
- See svlan id.