Linux Dummy network device

A dummy interface is used by TCP/IP to assign an IP address to your machine, which is required for both SLIP and PPP. The reason for a dummy interface is simple: When you connect to an ISP, your IP address is often assigned dynamically, and you never know what the IP address will be in advance. This can cause problems for TCP/IP routines in your kernel that need to know an IP address to function properly. TCP/IP is happy when you assign an IP address—the dummy interface IP address—to your machine. The need for an IP address internally is most important when you are not connected to your ISP because many network-aware applications (such as email, newsreaders, and so on) need to have some IP address to connect to, even if it doesn’t lead anywhere. This dummy interface IP address does not conflict with the one assigned by your ISP.

# modprobe dummy
# ifconfig dummy0 1.2.3.4 netmask 255.0.0.0

# modprobe dummy -o dummy1
# ifconfig dummy1 4.3.2.1 netmask 255.255.0.0

if you need to create 5 dummy interfaces , you can use this command :

# modprobe dummy numdummies=5