Loopback

The loopback interface is a virtual, software-based network interface. All traffic sent to it loops back and only targets services on the local host.

Note

Only one loopback lo interface is allowed per operating system. If you require multiple virtual interfaces, use the Dummy interface type.

Configuration

Common interface configuration

set interfaces loopback <interface> address <address>

Configure one or more interface IP addresses.

<address> supports IPv4 and IPv6 in CIDR notation. For example, use 192.0.2.1/24 for IPv4 or 2001:db8::1/64 for IPv6.

Example:

set interfaces loopback lo address 192.0.2.1/24
set interfaces loopback lo address 2001:db8::1/64

set interfaces loopback <interface> description <description>

Configure a clear, descriptive alias for the interface.

This alias appears in the show interfaces command and SNMP-based monitoring tools.

Example:

set interfaces loopback lo description 'This is an interface running on VyOS.'

Operation

show interfaces loopback

Show brief interface information.

vyos@vyos:~$ show interfaces loopback
Codes: S - State, L - Link, u - Up, D - Down, A - Admin Down
Interface        IP Address                        S/L  Description
---------        ----------                        ---  -----------
lo               127.0.0.1/8                       u/u
                 ::1/128

show interfaces loopback lo

Show detailed interface information.

vyos@vyos:~$ show interfaces loopback lo
lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever

    RX:  bytes    packets     errors    dropped    overrun      mcast
           300          6          0          0          0          0
    TX:  bytes    packets     errors    dropped    carrier collisions
           300          6          0          0          0          0