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:lastproofread: 2026-01-23
.. _dummy-interface:
#####
Dummy
#####
A dummy interface is a virtual network interface that operates like the
loopback interface, accepting traffic and routing it back to the local host.
Unlike the loopback interface, which is limited to one per system and reserved
for internal system use, multiple dummy interfaces can be created, removed, and
managed without impacting core operations.
As a software-based interface, the dummy interface does not depend on physical
link state and remains active as long as the operating system is running.
Dummy interfaces are commonly used in environments with multiple redundant
uplinks (e.g., a server connected to two different switches), where assigning a
management IP address to a specific physical interface is risky. If that
interface fails, the management IP address becomes unreachable.
Assigning the management IP address to a dummy interface and advertising it
over all available physical links ensures the address remains reachable as long
as at least one physical path is active.
Dummy interfaces are also used for testing and simulation purposes.
*************
Configuration
*************
Common interface configuration
==============================
.. cmdinclude:: /_include/interface-address.txt
:var0: dummy
:var1: dum0
.. cmdinclude:: /_include/interface-description.txt
:var0: dummy
:var1: dum0
.. cmdinclude:: /_include/interface-disable.txt
:var0: dummy
:var1: dum0
.. cmdinclude:: /_include/interface-vrf.txt
:var0: dummy
:var1: dum0
*********
Operation
*********
.. opcmd:: show interfaces dummy
Show brief interface information.
.. code-block:: none
vyos@vyos:~$ show interfaces dummy
Codes: S - State, L - Link, u - Up, D - Down, A - Admin Down
Interface IP Address S/L Description
--------- ---------- --- -----------
dum0 172.18.254.201/32 u/u
.. opcmd:: show interfaces dummy <interface>
Show detailed interface information.
.. code-block:: none
vyos@vyos:~$ show interfaces dummy dum0
dum0: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default qlen 1000
link/ether 26:7c:8e:bc:fc:f5 brd ff:ff:ff:ff:ff:ff
inet 172.18.254.201/32 scope global dum0
valid_lft forever preferred_lft forever
inet6 fe80::247c:8eff:febc:fcf5/64 scope link
valid_lft forever preferred_lft forever
RX: bytes packets errors dropped overrun mcast
0 0 0 0 0 0
TX: bytes packets errors dropped carrier collisions
1369707 4267 0 0 0 0
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