How to create a virtual network interface in Ubuntu?

Question

I'm testing a network program on Ubuntu. Is there any way to create a virtual network interface in Ubuntu. Something like lo is good, but unfortunately there is bunch of packets on lo with 127.0.0.1 as source and destination IP addrress.

Answer 1

USE CASE: To create a persistent VIP address in a server to function as a 'loopback' address

Change to /etc/systemd/network/ directory

user@server:~$ cd /etc/systemd/network/

Create two files, 'vip.netdev' and 'vip.network'

user@server:/etc/systemd/network$ touch vip.netdev vip.network

Show the newly created files

user@server:/etc/systemd/network$ ls
vip.netdev  vip.network

Edit the two files with your favorite editor to reflect the detail below

user@server:/etc/systemd/network$ more vip.netdev
[NetDev]
Name=vip
Kind=dummy

... and ...

user@server:/etc/systemd/network$ more vip.network
[Match]
Name=vip

[Network]
Address=172.16.1.23 (or whatever address you so choose)
Mask=255.255.255.255
Broadcast=172.16.1.255 (match the Address x.x.x.255)

Enable the newly created VIP interface w/out rebooting the server

user@server:/etc/systemd/network$ systemctl restart systemd-networkd

Show the newly create VIP interface

user@server:/etc/systemd/network$ ifconfig
ens33: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 172.16.1.16  netmask 255.255.255.0  broadcast 172.16.1.255
        inet6 fe80::20c:29ff:fe9b:703f  prefixlen 64  scopeid 0x20<link>
        ether 00:0c:29:9b:70:3f  txqueuelen 1000  (Ethernet)
        RX packets 244  bytes 32605 (32.6 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 653  bytes 51807 (51.8 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 411  bytes 66247 (66.2 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 411  bytes 66247 (66.2 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

vip: flags=195<UP,BROADCAST,RUNNING,NOARP>  mtu 1500
        inet 172.16.1.23  netmask 255.255.0.0  broadcast 172.16.255.255
        inet6 fe80::d0a7:56ff:fe83:95ff  prefixlen 64  scopeid 0x20<link>
        ether d2:a7:56:83:95:ff  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 7  bytes 490 (490.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

... or ...

user@server:/etc/systemd/network$ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 00:0c:29:9b:70:3f brd ff:ff:ff:ff:ff:ff
    inet 172.16.1.16/24 brd 172.16.1.255 scope global ens33
       valid_lft forever preferred_lft forever
    inet6 fe80::20c:29ff:fe9b:703f/64 scope link
       valid_lft forever preferred_lft forever
3: vip: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default qlen 1000
    link/ether d2:a7:56:83:95:ff brd ff:ff:ff:ff:ff:ff
    inet 172.16.1.23/16 brd 172.16.255.255 scope global vip
       valid_lft forever preferred_lft forever
    inet6 fe80::d0a7:56ff:fe83:95ff/64 scope link
       valid_lft forever preferred_lft forever

Answer 2

You can add another loopback interface using following command:

ip link add name mylo type dummy
ifconfig mylo up

Use mylo as loopback interface.