Creating or editing a GRE interface
The GRE protocol allows encapsulating IP traffic in a point-to-point IP tunnel. This allows, for example, routing networks from one site to another through a GRE tunnel without having to declare this routing method on all routers in between.
GRE tunnels are not encrypted natively: they merely encapsulate. GRE traffic can however be made to go through an IPsec tunnel.
To create or modify a virtual GRE interface, click on the GRE interfaces tab.
Button bar
| Search | Search that covers interfaces. |
| Add | Adds a new interface. An added interface (sending of a command) is effective only if its fields Name, IP address, Network mask, Tunnel source and Tunnel destination have been entered. |
| Delete | Deletes one or several selected interfaces. Use the keys Ctrl/Shift + Delete to delete several interfaces. |
| Check usage | Represented by the icon  , this button indicates whether the selected interface is being used elsewhere in the configuration. |
| Apply | Applies the configuration of the IPsec interfaces. |
| Cancel | Cancels the configuration of the IPsec interfaces. |
Interactive features
Some operations listed in the taskbar can be performed by right-clicking on the table of GRE interfaces:
- Add,
- Delete,
- Check usage.
Presentation of the table
The grid presents, in the form of columns, the information that is defined when creating a virtual GRE interface:
| Status | Status of the interfaces:
|
| Name (mandatory) | Name the GRE interface. |
| IPv4 address and mask (mandatory) | Enter the IP address/network mask pair that describes the virtual interface created. The mask format can be decimal (e.g., 255.255.255.252) or CIDR (e.g., %30). |
| Protected | This column is hidden by default. If you wish to show it:
When the column is shown, double-click on the corresponding cell to change the interface type:
|
| Tunnel source (mandatory) | Select the outgoing interface of traffic using the tunnel. In general, this would be the firewall’s “out” interface or a bridge. |
| Tunnel destination (mandatory) | Select the object representing the tunnel’s remote endpoint. This is a host object that presents the public IP address of the remote firewall. |
| Comments(optional) | Any text. |
Enabled: Double-click to enable the created interface.
Disabled: The interface is not in operation. The line will be grayed out in order to reflect this.