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M. Rostami
Asked: 2021-01-19 02:00:56 +0800 CST

KVM add public IP to a virtual machine

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I got a new dedicated server and installed KVM on it. I've created a virtual machine but I got some problems managing public IP to that VM. In addition, the Ubuntu 18.0.4 LTS server has installed on the host VM.

The host network details

ifconfig:

eno1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 88.44.31.30  netmask 255.255.255.255  broadcast 0.0.0.0
        inet6 fe81::b62e:99fd:fecd:fd13  prefixlen 64  scopeid 0x20<link>
        inet6 2a02:4f8:232:1b07::2  prefixlen 64  scopeid 0x0<global>
        ether b2:2e:99:fb:3b:aa  txqueuelen 1000  (Ethernet)
        RX packets 2934329  bytes 1525163180 (1.5 GB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 2799211  bytes 3794187248 (3.7 GB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
        device interrupt 16  memory 0x51200000-51220000  

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 246437  bytes 3598125972 (3.5 GB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 246437  bytes 3598125972 (3.5 GB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

virbr0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.122.1  netmask 255.255.255.0  broadcast 192.168.122.255
        ether 52:53:0b:a6:6f:f0  txqueuelen 1000  (Ethernet)
        RX packets 15954  bytes 1189621 (1.1 MB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 27979  bytes 283208200 (283.2 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

vnet0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet6 fe81::fc50:56af:fbb0:6aa4  prefixlen 64  scopeid 0x20<link>
        ether fe:50:56:00:67:ab  txqueuelen 1000  (Ethernet)
        RX packets 870  bytes 100801 (100.8 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 21441  bytes 2188836 (2.1 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

/etc/netplan/01-netcfg.yaml:

network:
  version: 2
  renderer: networkd
  ethernets:
    eno1:
      addresses:
        - 88.44.31.30/32
        - 2a02:4f8:232:1b07::2/64
      routes:
        - on-link: true
          to: 0.0.0.0/0
          via: 88.44.31.1
      gateway6: fe81::1
      nameservers:
        addresses:
          - 213.133.98.98
          - 213.133.99.99
          - 213.133.100.100
          - 2a01:4f8:0:1::abd:9912
          - 2a01:4f8:0:1::abd:1022
          - 2a01:4f8:0:1::abd:9844

route -n:

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         88.44.31.1     0.0.0.0         UG    0      0        0 eno1
192.168.122.0   0.0.0.0         255.255.255.0   U     0      0        0 virbr0

The VM network details

ifconfig:

enp1s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.122.178  netmask 255.255.255.0  broadcast 192.168.122.255
        inet6 fe81::fc50:bbaf:fab0:6aa5  prefixlen 64  scopeid 0x20<link>
        ether 00:bb:56:aa:67:ab  txqueuelen 1000  (Ethernet)
        RX packets 797  bytes 302823 (302.8 KB)
        RX errors 0  dropped 590  overruns 0  frame 0
        TX packets 165  bytes 19312 (19.3 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 90  bytes 6966 (6.9 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 90  bytes 6966 (6.9 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

/etc/netplan/00-installer-config.yaml:

network:
  ethernets:
    enp1s0:
      dhcp4: true
  version: 2

route -n:

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.122.1   0.0.0.0         UG    100    0        0 enp1s0
192.168.122.0   0.0.0.0         255.255.255.0   U     0      0        0 enp1s0
192.168.122.1   0.0.0.0         255.255.255.255 UH    100    0        0 enp1s0

The ISP gives me the following address:

address 88.44.31.10
netmask 255.255.255.224
gateway 88.44.31.1

Therefore, I need to access the VM from the outside/internet by 88.44.31.10 but dunno how to configure the host and the VM.

Thanks in advance.

kvm

1 Answers

  1. You will need to create a bridge on your external interface. Then you can have an device&IP on that bridge for your host, but also connect your guest to it to work on the same externally facing network.

    An example of such a configuration can be found on the netplan.io example page.

    You can later on go bigger considering OpenVswitch as an alternative, but that will be more complex and therefore only useful if you need it's advanced features.

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