---
lastproofread: '2023-01-20'
---

(loopback-interface)=

# Loopback

The loopback networking interface is a virtual network device implemented
entirely in software. All traffic sent to it "loops back" and just targets
services on your local machine.

:::{note}
There can only be one loopback `lo` interface on the system. If
you need multiple interfaces, please use the {ref}`dummy-interface`
interface type.
:::

:::{hint}
A loopback interface is always up, thus it could be used for
management traffic or as source/destination for and {abbr}`IGP (Interior
Gateway Protocol)` like {ref}`routing-bgp` so your internal BGP link is not
dependent on physical link states and multiple routes can be chosen to the
destination. A {ref}`dummy-interface` Interface should always be preferred
over a {ref}`loopback-interface` interface.
:::

## Configuration

### Common interface configuration

```{eval-rst}
.. cmdincludemd:: /_include/interface-address.txt
   :var0: loopback
   :var1: lo
```

```{eval-rst}
.. cmdincludemd:: /_include/interface-description.txt
   :var0: loopback
   :var1: lo
```

## Operation

```{eval-rst}
.. opcmd:: show interfaces loopback

   Show brief interface information.

   .. code-block:: none

     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
```

```{eval-rst}
.. opcmd:: show interfaces loopback lo

   Show detailed information on the given loopback interface `lo`.

   .. code-block:: none

     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
```