How to add a loopback interface?

Question

I want to add two more loopback interfaces.

I used the following command:

ifconfig lo: 127.0.0.2 netmask 255.0.0.0 up

and type in ifconfig, i can see the loopback address was added.

But if i want to add one more interface... (for example 127.0.0.3) the previous interface (127.0.0.2) was overwritten.

Also when i look in /etc/network/interfaces i see no entry.

How can i add multiple loopback interfaces permanently?

Answer 1

It depends what you want lo or lo: which is an interface alias.

ifconfig lo:0 127.0.0.2 netmask 255.0.0.0 up
ifconfig lo:1 127.0.0.3 netmask 255.0.0.0 up
ifconfig lo:2 127.0.0.4 netmask 255.0.0.0 up

works. If you want to have more IP's on lo use

route add -host 127.0.0.3 dev lo
route add -host 127.0.0.4 dev lo
route add -host 127.0.0.5 dev lo

works too. If you want to remove it, use:

route del -host 127.0.0.3
route del -host 127.0.0.4
route del -host 127.0.0.5

Answer 2

如果您继续使用，ifconfig lo...您不是在创建新界面，而是在覆盖之前的界面。您可以尝试编辑您的接口文件：

sudo vim /etc/network/interfaces

我的看起来像这样：

# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback

因此，您可以尝试修改它以创建新接口：

# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback
auto lo2
iface lo2 inet loopback
auto lo3

然后，重新启动网络或整个系统，并尝试与新接口交互：

sudo ifconfig lo2/lo3 etc...

我不认为这实际上有效。根据 driver/net/loopback.c，您只能在每个命名空间上拥有“lo”设备。“dummy”设备可以做你需要的一切，“sudo ip link add name loop1 type dummy” (4认同)
这不起作用：`找不到设备“lo1”` (2认同)

Answer 3

要永久添加多个环回接口，必须对虚拟驱动程序进行额外检查。

虚拟驱动程序用于制作多个环回设备，而不是
为一台设备创建多个别名，并附加不同的 IP。

此行添加另一个名为的环回loop1, loop2, loop3：

sudo ip link add name loop1 type dummy
sudo ip link add name loop2 type dummy
sudo ip link add name loop3 type dummy

dummy在运行上述命令之前请检查内核模块是否已加载：

sudo lsmod | grep dummy