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VPS: Fixing network problems that occur after migration

In individual cases, the name of the network device is changed in the network configuration file of your operating system as part of the migration of your server.

To correct the network configuration settings, proceed as follows:

Operating systems without static configuration of IP addresses

  • To display information on all network interfaces, enter the following command:

    [root@localhost ~]# ip addr


    In this example, the name of the network interface is ens192:

    [root@localhost ~]# ip addr

    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: ens192: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 00:50:56:2c:95:c9 brd ff:ff:ff:ff:ff:ff:ff
    altname enp11s0
    inet 82.165.19.21/32 scope global dynamic noprefixroute ens192
    valid_lft 40221sec preferred_lft 40221sec
    inet6 2001:8d8:1800:194::1/128 scope global dynamic noprefixroute
    valid_lft 3231sec preferred_lft 3231sec
    inet6 fe80::6c11:4b6b:f43d:adad/64 scope link noprefixroute
    valid_lft forever preferred_lft forever

  • If you are using Ubuntu 20.04 or Ubuntu 22.04, you must also check whether Netplan is being used. To do this, change to the /etc/netplan directory and check whether there is a configuration file in this directory. To do this, enter the following commands:

    [root@localhost ~]# cd /etc/netplan
    [root@localhost ~]# ls

  • Open the configuration file of your network with the vi editor.

    CentOS 7

    root@localhost ~]# vi /etc/sysconfig/network-scripts/ifcfg-ens192


    Ubuntu 18.04, Ubuntu 20.04, Debian 10, 11 and Debian 12

    [root@localhost ~]# vi /etc/network/interfaces


    CentOS Stream 8, AlmaLinux 8 and Rocky Linux 8

    [root@localhost ~]# vi /etc/sysconfig/network-scripts/ifcfg-NETZWERKINTERFACE

    Example:

    [root@localhost ~]# vi /etc/sysconfig/network-scripts/ifcfg-ens192


    Ubuntu 20.04 and 22.04 with Netplan

    [root@localhost ~]# vi /etc/netplan/01-netcfg.yaml


    CentOS Stream 9, AlmaLinux 9 and Rocky Linux 9

    [root@localhost ~]# vi /etc/NetworkManager/system-connections/NETZWERKINTERFACE.nmconnection

    Example:

    [root@localhost ~]# vi /etc/NetworkManager/system-connections/ens192.nmconnection

Notes
  • The vi editor has an insert mode and a command mode. You can call up insert mode with the i key. In this mode, the characters entered are immediately inserted into the text. To call up command mode, press ESC. If you use command mode, your keyboard input is interpreted as a command.
  • To exit vi and save the file, enter the command :wq and then press Enter.
  • Check the entries and correct the name of the specified network interface.
  • To save the changes, press the ESC key, then enter :wq and press Enter.

Operating systems with static configuration of IP addresses

  • To display information on all network interfaces, enter the following command:

    [root@localhost ~]# ip addr

    In this example, the name of the network interface is ens192:

    [root@localhost ~]# ip addr

    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: ens192: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 00:50:56:2c:95:c9 brd ff:ff:ff:ff:ff:ff:ff
    altname enp11s0
    inet 82.165.19.21/32 scope global dynamic noprefixroute ens192
    valid_lft 40221sec preferred_lft 40221sec
    inet6 2001:8d8:1800:194::1/128 scope global dynamic noprefixroute
    valid_lft 3231sec preferred_lft 3231sec
    inet6 fe80::6c11:4b6b:f43d:adad/64 scope link noprefixroute
    valid_lft forever preferred_lft forever

  • If you are using Ubuntu 20.04 or Ubuntu 22.04, you must also check whether Netplan is being used. To do this, change to the /etc/netplan directory and check whether there is a configuration file in this directory. To do this, enter the following commands:

    [root@localhost ~]# cd /etc/netplan
    [root@localhost ~]# ls

  • Open the configuration file for your network using the vi editor.

    CentOS 7

    [root@localhost ~]# vi /etc/sysconfig/network-scripts/ifcfg-ens192


    Ubuntu 18.04, Ubuntu 20.04 without Netplan, Debian 10, 11 and Debian 12

    [root@localhost ~]# vi /etc/network/interfaces


    CentOS Stream 8, AlmaLinux 8 and Rocky Linux 8

    [root@localhost ~]# vi /etc/sysconfig/network-scripts/ifcfg-ens192


    Ubuntu 20.04 and 22.04 with Netplan

    [root@localhost ~]# vi /etc/netplan/01-netcfg.yaml


    CentOS Stream 9, AlmaLinux 9 and Rocky Linux 9

    [root@localhost ~]# vi /etc/NetworkManager/system-connections/ens192.nmconnection


    or

    [root@localhost ~]# vi /etc/NetworkManager/system-connections/eth0.nmconnection

Notes
  • The vi editor has an insert mode and a command mode. You can call up insert mode with the i key. In this mode, the characters entered are immediately inserted into the text. To call up command mode, press ESC. If you use command mode, your keyboard input is interpreted as a command.
  • To exit vi and save the file, enter the command :wq and then press Enter.
  • Check the entries and correct the name of the specified network interface.
  • Replace the specified gateway. To do this, use the main IPv4 address and replace the numbers after the third dot with the number 1. Use the following format:

    IP address: 123.456.78.91

    IPv4 gateway: 123.456.78.1

    Example:
    The server uses the main IPv4 address 82.165.34.29. In this case, the gateway 82.165.34.1 must be entered.
     
  • Only applies to Ubuntu 18.04, Ubuntu 20.04, Debian 10, 11 and Debian 12: Make sure that the netmask 255.255.255.255 is used.

  • Replace the IPv6 settings:
     

    CentOS 7

    IPV6INIT=yes
    IPV6_FAILURE_FATAL=no
    IPV6_AUTOCONF=yes
    DHCPV6C=yes


    CentOS Stream 8, AlmaLinux 8 and Rocky Linux 8

    IPV6INIT=yes
    IPV6_FAILURE_FATAL=no


    CentOS Stream 9, Alma Linux 9 and Rocky Linux 9

    [ipv6]
    addr-gen-mode=eui64
    method=auto


    Ubuntu 18.04, Ubuntu 20.04 without Netplan, Debian 10, 11 and Debian 12

    iface ens192 inet6 manual
        pre-up sleep 5
        up dhclient -6 -nw -v ens192
        down dhclient -6 -r -v ens192


    Ubuntu 20.4 and Ubuntu 22.04 with Netplan

            dhcp6: true

  • To save the changes, press the [ESC] key, then enter :wq and press Enter.

  • Restart the server so that the changes are applied. To do this, enter the following command:

    root@localhost:~# systemctl reboot

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