How to create a virtual network interface in Ubuntu?

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.

2 Answers

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

You can add another loopback interface using following command:

ip link add name mylo type dummy
ifconfig mylo up

Use mylo as loopback interface.