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diff --git a/docs/configuration/interfaces/loopback.md b/docs/configuration/interfaces/loopback.md new file mode 100644 index 00000000..37da5399 --- /dev/null +++ b/docs/configuration/interfaces/loopback.md @@ -0,0 +1,80 @@ +--- +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 +``` |