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76 lines
2.6 KiB
ReStructuredText
76 lines
2.6 KiB
ReStructuredText
.. _loopback-interface:
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########
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Loopback
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########
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The loopback networking interface is a virtual network device implemented
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entirely in software. All traffic sent to it "loops back" and just targets
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services on your local machine.
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.. note:: There can only be one loopback ``lo`` interface on the system. If
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you need multiple interfaces, please use the :ref:`dummy-interface`
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interface type.
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.. hint:: A lookback interface is always up, thus it could be used for
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management traffic or as source/destination for and :abbr:`IGP (Interior
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Gateway Protocol)` like :ref:`bgp` so your internal BGP link is not dependent
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on physical link states and multiple routes can be chosen to the
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destination. A :ref:`dummy-interface` Interface should always be preferred
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over a :ref:`loopback-interface` interface.
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Configuration
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=============
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Address
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-------
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.. cfgcmd:: set interfaces loopback lo address <address>
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Configure Loopback interface `lo` with one or more interface addresses.
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Address can be specified multiple times as IPv4 and/or IPv6 address, e.g.
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192.0.2.1/24 and/or 2001:db8::1/64.
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Link Administration
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-------------------
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.. cfgcmd:: set interfaces loopback lo description <description>
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Assign given `<description>` to interface `lo`. Description will also be
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passed to SNMP monitoring systems.
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Operation
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=========
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.. opcmd:: show interfaces loopback
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Show brief interface information.
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.. code-block:: none
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vyos@vyos:~$ show interfaces loopback
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Codes: S - State, L - Link, u - Up, D - Down, A - Admin Down
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Interface IP Address S/L Description
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--------- ---------- --- -----------
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lo 127.0.0.1/8 u/u
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::1/128
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.. opcmd:: show interfaces loopback lo
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Show detailed information on given loopback interface `lo`.
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.. code-block:: none
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vyos@vyos:~$ show interfaces ethernet eth0
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lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
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link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
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inet 127.0.0.1/8 scope host lo
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valid_lft forever preferred_lft forever
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inet6 ::1/128 scope host
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valid_lft forever preferred_lft forever
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RX: bytes packets errors dropped overrun mcast
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300 6 0 0 0 0
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TX: bytes packets errors dropped carrier collisions
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300 6 0 0 0 0
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