To configure a loopback interface for an Edge:

Prerequisites

For information about the rules and notes that you must consider before you configure a loopback interface, see Loopback Interfaces—Limitations.

Procedure

  1. In the SD-WAN service of the Enterprise portal, go to Configure > Edges.
  2. Click the link to an Edge for which you want to configure the loopback interface or click the View link in the Device column of the Edge. The configuration options for the selected Edge are displayed in the Device tab.
  3. Scroll down to the Connectivity category and click Loopback Interfaces.
  4. Click + Add and in the Add Loopback pop-up window, configure the required loopback settings as described in the following table.
    Field Description
    Interface ID Enter a unique ID for the loopback interface. The ID must be unique across all segments within an Edge and must start from 1, as Zero (0) is not supported.
    Segment Select a segment from the drop-down list. The loopback interface belongs to the selected segment.
    ICMP Echo Response Select the check box to enable the loopback interface to respond to ICMP echo messages.
    IPv4 Settings
    Addressing Type By default, the addressing type is Static and you cannot modify the type.
    IP Address Enter the IPv4 address for the loopback interface.
    CIDR Prefix The CIDR prefix for the loopback interface IPv4 address. The default value is /32. You cannot modify the default value.
    Advertise Select the check box to advertise the loopback interface to other branches in the network.
    OSPF
    Select the check box and choose an OSPF Area from the drop-down list. The loopback interface IP address is advertised in the selected OSPF area.
    Note: The OSPFv2 configuration supports only IPv4. The OSPFv3 configuration supports only IPv6, which is only available in the 5.2 release.
    Note: This option is enabled only when you have configured OSPF for the segment that you have selected for the loopback interface. OSPF is not supported on Sub Interfaces, and it is not supported on non Global Segments.

    For more information on OSPF settings and OSPFv3, see Activate OSPF for Profiles.
    IPv6 Settings
    Addressing Type By default, the addressing type is Static and you cannot modify the type.
    IP Address Enter the IPv6 address for the loopback interface.
    CIDR Prefix The CIDR prefix for the loopback interface IP address. The default value is /128. You cannot modify the default value.
    Note: You can select the Active check boxes for the IPv4 and IPv6 settings, to enable the corresponding addressing type for the Interface. By default, the option is enabled for IPv4 settings.
  5. Click Add.
  6. Click Save Changes.

Results

The loopback interface is listed in the Loopback Interfaces area.

At any point in time, you can choose to edit the loopback interface settings by clicking the Address link, except CIDR Prefix and Interface ID.

If you delete a loopback interface, the Source Interface field for all the services for which you have selected the loopback interface, is reset to Auto.

In addition, following are two more scenarios based on which the Source Interface for the various services is reset to Auto:
  • If the loopback interface ID is not found in the Edge.
  • If you use older versions of APIs to configure the Edge, sometimes the Edge may not receive the key for source IP address for the services.
When the Source Interface field for any service is set to Auto, the Edge selects the source interface based on the following criteria:
  • Any non-WAN interface that is advertised is prioritized.
  • Among the non-WAN interfaces that are advertised, the source interface selection is based on the following order of priority—Loopback interfaces, VLAN interfaces, or any routed interfaces.
  • If there are more than one interfaces of the same type configured and advertised, the interface with the lowest interface ID is selected.

    For example, if you have two loopback interfaces (LO3 and LO4), one VLAN interface (VLAN2), and two routed interfaces (GE1 and GE2) configured and advertised, and if the Source Interface field for any service is set to Auto, the Edge selects LO3 as the source interface.

What to do next

Once you configure the loopback interface for an Edge, you can select the interface as the source interface for the following services:
Services/Settings For details, refer to ...
Orchestrator Management Traffic Configure Management Traffic for Edges
Authentication Settings Configure Authentication Settings for Profiles
DNS Settings Configure DNS for Profiles
Netflow Settings Configure Netflow Settings for Edges
Syslog Settings Configure Syslog Settings for Edges
BGP Settings Configure BGP from Edge to Underlay Neighbors for Profiles
NTP Settings Configure NTP Settings for Edges
Note:

When the Edge transmits the traffic, the packet header will have the IP address of the selected source interface, whereas the packets can be sent through any interface based on the destination route.