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Sam Forma
Asked: 2020-12-18 15:54:59 +0800 CST

Ubuntu Server 20.10 - virtual interfaces in netplan

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I am trying to add a virtual interface to a bare metal Ubuntu Server 20.10 installation.

I've read that in pre version 20 this wasn't possible in netplan, and that people were reverting to ifup/ifdown. But this is supposed to be possible with what I have.

I am trying to give my server a second interface so I can bind a pihole docker container to said interface.

I see in the netplan docs various interface types, and the closest one is a vlan type, but it doesn't seem that type works with untagged vlans.

In any case, I appreciate any help you can give me.

networking interface netplan

4 Answers

  1. I'm going to assume that by "virtual interface" you mean that you want to have a main interface (Example: "eth0"), which may or may not have an address on one subnet, and you want to create an interface labeled differently (Example: "eth0:0") with an address on a different subnet.

    Prior to netplan version 0.100, this was not supported. However, version 0.100 added the lifetime and label properties to the addresses values.

    You can check your installed netplan version with the following command: dpkg -l | grep netplan

    Here is an example .yaml that will attempt to use dhcp to assign an IP address to the eth0 interface, and will assign the static IP address 192.168.55.151/24 to the virtual interface labeled eth0:0:

    network:
  version: 2
  renderer: networkd
  ethernets:
    eth0:
      dhcp6: no
      dhcp4: yes
      optional: true
      addresses: 
        - 192.168.55.151/24: 
            lifetime: 0
            label: "eth0:0"

    This will produce the following results (of course eth0 would have an IP if it were connected to a DHCP server):

    odroid@odroid:~$ ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet6 fe80::21e:6ff:fe48:114  prefixlen 64  scopeid 0x20<link>
        ether 00:1e:06:48:01:14  txqueuelen 1000  (Ethernet)
        RX packets 6389  bytes 966018 (966.0 KB)
        RX errors 0  dropped 1649  overruns 0  frame 0
        TX packets 531  bytes 160364 (160.3 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
        device interrupt 21  

eth0:0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.55.151  netmask 255.255.255.0  broadcast 192.168.55.255
        ether 00:1e:06:48:01:14  txqueuelen 1000  (Ethernet)
        device interrupt 21  

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 1  (Local Loopback)
        RX packets 31816  bytes 2259360 (2.2 MB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 31816  bytes 2259360 (2.2 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

odroid@odroid:~$ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
    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: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 00:1e:06:48:01:14 brd ff:ff:ff:ff:ff:ff
    inet 192.168.55.151/24 brd 192.168.55.255 scope global deprecated eth0:0
       valid_lft forever preferred_lft forever
    inet6 fe80::21e:6ff:fe48:114/64 scope link 
       valid_lft forever preferred_lft forever
    • 3

  2. "Virtual interface" can refer to a variety of different technologies. Normally, containers are attached to a bridge. You can create bridges in netplan, using syntax such as:

    network:
  version: 2
  bridges:
    dockernet:
      addresses: [10.1.1.1/24]
    • 1

  3. Update to edited question.

    Netplan can assign multiple addresses to a single interface and does not support interface aliases (e.g. eth0:0).

    network:
    version: 2
    renderer: networkd
    ethernets:
        enp3s0:
         addresses:
             - 10.100.1.38/24
             - 10.100.1.39/24
         gateway4: 10.100.1.1

    Taken from this link https://netplan.io/examples/#using-multiple-addresses-on-a-single-interface

    Docker try's to bind to all interfaces by default. An ip address on a given interface can by specified. docker run -d -p 10.0.0.1:8080:80 nginx

    • 1

  4. Maybe this will do the job: https://netplan.io/examples/#attaching-vlans-to-network-interfaces

    network:
version: 2
renderer: networkd
ethernets:
    mainif:
        match:
            macaddress: "de:ad:be:ef:ca:fe"
        set-name: mainif
        addresses: [ "10.3.0.5/23" ]
        gateway4: 10.3.0.1
        nameservers:
            addresses: [ "8.8.8.8", "8.8.4.4" ]
            search: [ example.com ]
vlans:
    vlan15:
        id: 15
        link: mainif
        addresses: [ "10.3.99.5/24" ]
    vlan10:
        id: 10
        link: mainif
        addresses: [ "10.3.98.5/24" ]
        nameservers:
            addresses: [ "127.0.0.1" ]
            search: [ domain1.example.com, domain2.example.com ]
    • 0