| lastproofread: | 2023-01-20 |
|---|
The dummy interface is really a little exotic, but rather useful nevertheless. Dummy interfaces are much like the :ref:`loopback-interface` interface, except you can have as many as you want.
Note
Dummy interfaces can be used as interfaces that always stay up (in the same fashion to loopbacks in Cisco IOS), or for testing purposes.
Hint
On systems with multiple redundant uplinks and routes, it's a good idea to use a dedicated address for management and dynamic routing protocols. However, assigning that address to a physical link is risky: if that link goes down, that address will become inaccessible. A common solution is to assign the management address to a loopback or a dummy interface and advertise that address via all physical links, so that it's reachable through any of them. Since in Linux-based systems, there can be only one loopback interface, it's better to use a dummy interface for that purpose, since they can be added, removed, and taken up and down independently.
.. 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
.. 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 information on given `<interface>`
.. 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