# Loopback Interface Configuration

A loopback interface is a logical interface that emulates a physical interface on the device. A loopback interface is always in the up state as long as the device on which it resides it up. You configure a loopback interface with the name loopback.n, and assign an IP address to the interface. Like a physical interface, you must bind the loopback interface to a security zone.

### To Configure a Loopback Interface

1. On the Interface List page, select Loopback IF, click New, and then enter the necessary information:

Interface Name: Enter a number next to "loopback". This number identifies the loopback interface.

Zone: The name of the zone to which the loopback interface is bound.

IP Address/Netmask: Enter the IP address of the loopback interface and the subnet mask for the subnet on which the loopback interface IP address is located.

Manageable: Select this option to enable management of the device using the interface IP address.

Management Services:

WebUI: Select this option to enable management through the Web user interface (WebUI).

SNMP: Select this option to enable the use of SNMP. The device supports the SNMPv1 protocol (described in RFC-1157) and all relevant MIB II (Management Information Base II) groups defined in RFC-1213.

Telnet: Select this option to allow management through a terminal emulation program for TCP/IP networks such as the Internet. Telnet is a common way to remotely control a network device.

SSL: Select this option to allow the interface to receive HTTPS traffic for secure management of the device via the WebUI.

SSH: Select this option to enable management using a secure command shell (SSH). You can administer the device from an Ethernet connection or a dial-in modem using SSH.

Other Services:

Ping: Select this option to allow the device to respond to ICMP echo requests, or "pings". Ping is a utility that determines whether a specific IP address is accessible or not.

DNS Proxy: Select this option if you want the device to proxy (forward) DNS queries received on this interface to the appropriate DNS server as configured on the DNS Proxy Configuration page.

2. Click OK to save your changes and return to the Interface List.

A loopback interface allows a mapped IP (MIP) address to be accessed by a group of interfaces. Using a loopback interface, a node can reach a MIP host through one of several VPN tunnels. To allow interfaces to use the MIP on the loopback interface, you then configure the interfaces as members of the loopback interface group. The maximum number of members in a loopback interface group is 10. The loopback interface and its member interfaces must be in different IP subnets in the same zone. Any type of interface can be a member of a loopback interface group as long as the interface has an IP address. If you configure a MIP on both a loopback interface and on one of its member interfaces, the loopback interface configuration takes precedence.

### To Configure a Loopback Interface for MIP

1. On the Interface List page, select Loopback IF, click New, and then enter the necessary information:

Interface Name: Enter a number from 1 to 10 next to "loopback". This number identifies the loopback interface.

Zone: The name of the zone to which the loopback interface is bound.

IP Address/Netmask: Enter the IP address of the loopback interface and the subnet mask for the subnet on which the loopback interface IP address is located.

Manageable: Select this option to enable management of the device using the interface IP address.

Management Services:

WebUI: Select this option to enable management through the Web user interface (WebUI).

SNMP: Select this option to enable the use of SNMP. The device supports the SNMPv1 protocol (described in RFC-1157) and all relevant MIB II (Management Information Base II) groups defined in RFC-1213.

Telnet: Select this option to allow management through a terminal emulation program for TCP/IP networks such as the Internet. Telnet is a common way to remotely control a network device.

SSL: Select this option to allow the interface to receive HTTPS traffic for secure management of the device via the WebUI.

SSH: Select this option to enable management using a secure command shell (SSH). You can administer the device from an Ethernet connection or a dial-in modem using SSH.

Other Services:

Ping: Select this option to allow the device to respond to ICMP echo requests, or "pings". Ping is a utility that determines whether a specific IP address is accessible or not.

DNS Proxy: Select this option if you want the device to proxy (forward) DNS queries received on this interface to the appropriate DNS server as configured on the DNS Proxy Configuration page.

2. Click OK to save your changes and return to the Interface List. Click Apply to continue configuring the interface.

3. Configure the MIP for the loopback interface. See Mapped IP Address Configuration.

4. Configure each of the member interfaces, specifying the loopback interface as the loopback group for the interface. See Interface Configuration.