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.. _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 lookback 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:`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
=============
Address
-------
.. cfgcmd:: set interfaces loopback lo address <address>
Configure Loopback interface `lo` with one or more interface addresses.
Address can be specified multiple times as IPv4 and/or IPv6 address, e.g.
192.0.2.1/24 and/or 2001:db8::1/64.
Link Administration
-------------------
.. cfgcmd:: set interfaces loopback lo description <description>
Assign given `<description>` to interface `lo`. Description will also be
passed to SNMP monitoring systems.
Operation
=========
.. 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
.. opcmd:: show interfaces loopback lo
Show detailed information on given loopback interface `lo`.
.. code-block:: none
vyos@vyos:~$ show interfaces ethernet eth0
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
|
