Correct way of bringing network interface down in linux

Question

For example:

$ ifconfig dummy0 up
$ ifconfig dummy0 "192.168.1.190 netmask 255.255.255.0"

Calling ifconfig with no parameters shows the interface

dummy0    Link encap:Ethernet  HWaddr b6:1f:f3:92:6d:20  
      inet addr:192.168.1.190  Bcast:192.168.1.255  Mask:255.255.255.0
      inet6 addr: fe80::b41f:f3ff:fe92:6d20/64 Scope:Link
      UP BROADCAST RUNNING NOARP  MTU:1500  Metric:1
      RX packets:0 errors:0 dropped:0 overruns:0 frame:0
      TX packets:15 errors:0 dropped:0 overruns:0 carrier:0
      collisions:0 txqueuelen:0 
      RX bytes:0 (0.0 B)  TX bytes:1050 (1.0 KiB)

How can I bring the interface down so that it doesn't show up in

• ifconfig
• ifconfig -a
• ifconfig dummy0

without rmmod dummy

because dummy is used just for example purposes.

If there is no way to do that, what "throw-away" IP could I set to it and be safe from any trouble?

like

$ ifconfig dummy0 down
$ ifconfig dummy0 0.0.0.0

Solution 1

Flush the ip:

root@foo:~# ifconfig dummy0 192.168.55.1 netmask 255.255.255.0
root@foo:~# ifconfig dummy0 
dummy0    Link encap:Ethernet  HWaddr 5b:72:32:4f:92:c8  
          inet addr:192.168.55.1  Bcast:192.168.55.255  Mask:255.255.255.0
          UP BROADCAST RUNNING NOARP  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

root@foo:~# ip address flush dev dummy0
root@foo:~# ifconfig dummy0 down
root@foo:~# ifconfig dummy0 
dummy0    Link encap:Ethernet  HWaddr 5b:72:32:4f:92:c8
          BROADCAST NOARP  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

Solution 2

to bring interface dummy0 down

ip link set dummy0 down

to bring it up

ip link set dummy0 up

Solution 3

there is usually a ifdown script on the root shell.

/sbin/ifdown

Throw away IP addresses are out of question.
Unused interfaces should be shutdown.

Solution 4

I used this command to show all interfaces

ip a s

To disable dummy I use two commands (RHEL is so "fascinating")):

ifconfig dummy0 down

ip addr del "your ip" dev dummy0

That worked for me.

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Comments

[Karolis T.]

Doesn't remove it from ifconfig -a and ifconfig dummy0 still shows old IP address. The correct solution was to flush it, as per answer above.

[John Dyer]

"ifconfig", although still available in most distributions, has been considered deprecated for some time in favour of the "ip" tool.