Dummy
The dummy interface is really a little exotic, but rather useful nevertheless. Dummy interfaces are much like the Loopback 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.
Configuration
Common interface configuration
Configure interface <interface> with one or more interface addresses.
address can be specified multiple times as IPv4 and/or IPv6 address, e.g. 192.0.2.1/24 and/or 2001:db8::1/64
Example:
set interfaces dummy dum0 address 192.0.2.1/24
set interfaces dummy dum0 address 2001:db8::1/64
Set a human readable, descriptive alias for this connection. Alias is used by
e.g. the show interfaces command or SNMP based monitoring tools.
Example:
set interfaces dummy dum0 description 'This is an awesome interface running on VyOS'
Disable given <interface>. It will be placed in administratively down
(A/D) state.
Example:
set interfaces dummy dum0 disable
Place interface in given VRF instance.
See also
There is an entire chapter about how to configure a VRF, please check this for additional information.
Example:
set interfaces dummy dum0 vrf red
Operation
Show brief interface information.
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
Show detailed information on given <interface>
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