Example: Configuring Dynamic Subscriber Interfaces over VLANs

Requirements

• JunosE Release 7.1.0 or higher-numbered releases
• E Series router (ERX7xx models, ERX14xx models, the ERX310 router, the E120 router, or the E320 router)
• ASIC-based line modules that support Fast Ethernet or Gigabit Ethernet

Overview

Figure 1 shows the interface stack built for this configuration.

Figure 1: IP over VLAN over Ethernet Dynamic Subscriber Interface Configuration

Configuring Dynamic Subscriber Interfaces over VLANs

Step-by-Step Procedure

1. Configure the DHCP server.

   For instructions, see Configuring the DHCP Local Server .

2. Specify a Fast Ethernet, Gigabit Ethernet, or 10-Gigabit Ethernet port.
   host1(config)#interface gigabitEthernet 1/0

   Note: You can configure only the primary port, 0, on the Gigabit Ethernet module. The router automatically uses the redundant port if the primary port fails.

   Use the no version to remove IP from an interface. You must issue the no version from the highest level down; you cannot remove an interface or a subinterface if the one above it still exists.

3. Specify VLAN as the encapsulation method on the interface. This command creates the VLAN major interface.
   host1(config-if)#encapsulation vlan

   Use the no version to disable VLAN encapsulation on the interface.

4. Create a VLAN subinterface by adding a subinterface number to the interface identification command.
   host1(config-if)#interface gigabitEthernet 1/0.1
5. Assign a unique VLAN ID to the VLAN subinterface.
   host1(config-if)#vlan id 101

   You need to specify a VLAN ID number that is in the range 0–4095 and is unique within the Ethernet interface. Issue the vlan id command before you configure any upper-layer interfaces, such as IP.

   There is no no version.

6. Create the primary IP interface by assigning an IP address and mask to the VLAN subinterface (or make it unnumbered).
   host1(config-if)#ip address 192.168.2.10 255.255.255.0

   You must specify the layer 2 encapsulation before you set the IP address. Issuing this command creates the primary IP interface. You must create a primary IP interface on which to enable dynamic creation of subscriber interfaces.

   Use the no version to remove the IP address or to disable IP processing.

7. (Optional) Append the virtual router name to the subscriber interface in case of DSI configuration.
   host1(config-if)#ip auto-configure append-virtual-router-name
8. (Optional) Specify the source address of traffic that is destined for the primary IP interface.
   host1(config-if)#ip source-prefix 192.168.2.10 255.255.255.0

   You can use this command to configure a subscriber interface or a primary IP interface enabled for dynamic creation of subscriber interfaces to demultiplex traffic with the specified source address. Use the no version to remove the association between the interface and the specified IP source address and mask.