# Engine Editor > Interfaces > Loopback

Use this branch to define loopback IP addresses for Engines. Loopback IP addresses allow you to assign IP addresses that do not belong to any directly connected networks to the Engine.

Option | Definition
--- | ---
Bypass Default IP Address | Specifies how the source IP address for traffic sent from the Security Engine node is selected for tunnel interfaces that do not have IP addresses. Use Loopback IP Address in Unnumbered Tunnel Interface — Uses an IP address listed in the table as the source IP address of traffic sent from the Security Engine node. Use Default Outgoing IP Address in Unnumbered Tunnel Interface — Uses the default outgoing IP address defined in the Interface Options pane as the source IP address of traffic sent from the Security Engine node.
Loopback addresses table | Click Add Row to add a row to the table, or Remove Row to remove the selected row. Click Up or Down to move the selected item up or down.
Loopback Address | Enter the loopback IP address.
CVI Address (Clusters only) | Enter the loopback IP address for the cluster.
Node NDI Address (Clusters only) | Enter the node-specific loopback IP address.
OSPFv2 Area | To advertise the loopback IP address as an OSPFv2 internal route, double-click the cell, then select an OSPFv2 Area element.
Comment (Optional) | A comment for your own reference.