:lastproofread: 2026-01-23 .. _loopback-interface: ######## 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 :ref:`dummy-interface` interface type. .. hint:: The loopback interface is always operational, making it suitable for management traffic or as a stable source/destination for routing protocols such as BGP. This ensures internal routing sessions remain independent of physical link states. However, in most cases, the dummy interface is preferred over the loopback interface. ************* Configuration ************* Common interface configuration ============================== .. cmdinclude:: /_include/interface-address.txt :var0: loopback :var1: lo .. cmdinclude:: /_include/interface-description.txt :var0: loopback :var1: lo ********* 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 interface information. .. code-block:: none vyos@vyos:~$ show interfaces loopback lo lo: 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