Networks FAQ

How do I set up a firewall?
For every network interface, you can activate a firewall, which will block all incoming traffic by default. You must specify the rules that define which protocols will pass through the firewall, and which ports are enabled. For instructions on how to set up a firewall click here​
How does the IONOS firewall work?
The IONOS firewall offered in the DCD can be used for simple protection for THE hosts behind it. Once activated, all incoming traffic is blocked. The traffic can only pass through the ports that are explicitly enabled. Outgoing traffic is generally permitted. We recommend that you set up your own firewall VM, even for small networks. There are many cost-free options, including IP tables for Linux, pfSense FreeBSD, and various solutions for Windows.
See also: Activating a Firewall​
Do you have a DNS resolver?
Yes, there are DNS resolvers. Valid everywhere IP addresses for 1&1 resolvers are:
212.227.123.16
212.227.123.17
2001: 8d8: fe: 53: 72ec :: 1
2001: 8d8: fe: 53: 72ec :: 2
​
By adding a public DNS resolver you will provide a certain level of redundancy for your systems.
How do I create reverse DNS entries?
Please contact IONOS enterprise support team for personal assistance and more information on how to enable reverse DNS entries.
What is the IP address of my new server?
Once a server has been provisioned, you can find its IP address by following the procedure below:
Open VDC
Select the server, for which you wish to know the IP
Select the Network tab in the Inspector
Open the properties of the NIC
The IP address is listed in the Primary IP field.
See also: Reserve an IP Address​
How  can I connect multiple servers to the Internet?
The internet access element can connect to more than one server. Simply add multiple virtual machines to provide them all with internet access.
How can I get additional IPs for my server?
Users with the appropriate privileges can reserve and release additional IP addresses. Additional addresses are made available as part of a reserved consecutive IP block.
See also: Reserve an IP address​
How are IPs assigned by DHCP?
The public IP address assigned by DHCP will remain with your server. The IP address, however, may change when you deallocate your VM (power stop) or remove the network interface. We, therefore, recommend assigning reserved IPs when static IPs are required, such as for web servers.
Can I use my own DHCP server?
Yes, you can. To make sure that a network interface will be addressed from your own DHCP server, perform the following steps:
Open your data center
Select the NIC
Open the properties of the NIC in the Inspector
Clear the DHCP check box
This will disable the allocation of IPs to this NIC by IONOS DHCP, and then you can use your own DHCP server to allocate information for this interface.
How do I set up DHCP during a Linux installation?
We preset the subnet mask 255.255.255.255 for the DHCP allocation of public IPs. Unfortunately, this is not supported by all DHCP clients. You can perform network configuration at the operating system level or specify the netmask 255.255.255.0 using a configuration file.
How do I assign an IP address to a Linux server manually if DHCP fails?
DHCP configurations may fail during the installation of Linux distributions that do not support /32 subnet mask configurations. If this happens, the IP address can be assigned manually using the Remote Console.
Example
Network interface "eth0" is being assigned P address "46.16.73.50" and subnet mask "/24" ("255.255.255.0"). For the internet access to work, the IP address of the gateway (which is "46.16.73.1" in this example) must also be specified.
Command-line:
ifconfig eth0 46.16.73.50 netmask 255.255.255.0
route add default gw 46.16.73.1
Config file:
Modify the "interface" file in the "/etc/networking/" folder as follows:
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).
# The loopback network interface
auto lo
iface lo inet loopback
# The primary network interface
allow-hotplug eth0
iface eth0 inet static
address 46.16.73.50
netmask 255.255.255.0
gateway 46.16.73.1
Restart the interfaces:
ifdown eth0
ifup eth0
Which IP versions are supported?
We presently support IPv4, and are working on implementing IPv6 in the future.
What is the maximum bandwidth of your data centers?
Our data centers are connected as follows:
Data center Bandwidth
Location
Bandwidth in Gbit/s
Karlsruhe (DE)
4 x 10
Frankfurt (DE)
2 x 40 & 3 x 10
Berlin (DE)
2 x 10
London (UK)
2 x 10
Las Vegas (US)
3 x 10
Newark (US)
2 x 10
Logroño (ES)
2 x 10
What should I do if the network does not work?
First, attempt to log on to the VM with the Remote Console. If this is successful, please collect the information we will need to help you resolve the issue as described below.
We will need to know the following:
VM name
IP address
URLs of web applications running on your VM
We will need the output of the following commands:
Windows
ping Hostname
date /t
time /t
route print
ipconfig /all
netstat
netstat -e
route print or netstat -r
tracert and ping in/out
nslookup hostname DNS-Server
nslookup hostname DNS-Server
Linux
date
traceroute
ping Hostname
The output of the following commands can also give important clues:
arp -n
ip address list
ip route show
ip neighbour show
iptables --list --numeric --verbose
cat /etc/sysconfig/network-scrips/ifcfg-eth*
cat /etc/network/interfaces
cat /etc/resolv.conf
netstat tcp --udp --numeric -a
Script (for Linux-based VMs)
We have prepared a ready-made script that helps gather the relevant information. The script provides both screen output and a log file which you can forward to us.
Use the script with the additional parameter -p
You will be able to observe the commands as they are being executed, and take screenshots as needed.
What should I do if the Remote Console does not work?
If you are using the Java-based edition of the Remote Console, please ensure that you have the latest Java version installed and the following ports released:
80 (HTTP),
443 (HTTPS),
5900 (VNC).
The Remote Console becomes available immediately once the server is provisioned.
Is there a detailed traffic overview available?
There is no traffic overview screen in the user interface currently.
Customers can use either Traffic or Utilization endpoints of the Billing API to get details about their traffic usage.
Traffic
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curl -X GET "https://api.ionos.com/billing/:contract/traffic/?output=all" -H "accept: application/json" -H "Authorization: Basic ******"
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Utilization
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curl -X GET "https://api.ionos.com/billing/:contract/utilization/?type=TRAFFIC" -H "accept: application/json" -H "Authorization: Basic ******"
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More information in Swagger: https://api.ionos.com/billing/doc/​
How can I configure VirtIO settings in Windows?
Please use the configuration below to ensure the stability and performance of the network connections on the operating system side. We suggest that you first check the current settings to see if any adjustments are necessary.
How to verify the current network configuration
1.Open Device Manager
2.Open the network adapter section where you can see all your connected virtual network cards named “Red Hat VirtIO Ethernet Adapter”. Now open the Properties dialog and go to the “Advanced” tab.
3.Verify that your settings match those listed below; if not, follow the guidelines later in this guide to update them accordingly.
"Init.MTUSize"="1500"
"IPv4 Checksum Offload"="Rx & Tx Enabled"
"Large Send Offload V2 (IPv4)"="Enabled"
"Large Send Offload V2 (IPv6)"="Enabled"
"Offload.Rx.Checksum"="All"
"Offload.Tx.Checksum"="All"
"Offload.Tx.LSO"="Maximal"
"TCP Checksum Offload (IPv4)"="Rx & Tx Enabled"
"TCP Checksum Offload (IPv6)"="Rx & Tx Enabled"
"UDP Checksum Offload (IPv4)"="Rx & Tx Enabled"
"UDP Checksum Offload (IPv6)"="Rx & Tx Enabled"
Manual adjustments in the Properties dialog are not saved to the registry. To make any persistent changes, follow the guidelines in the following section.
How to update the network configuration
Once you determine that your system needs an update (see the “Verifying current network configuration” above), one of the following actions must be taken to adjust the settings:
Online update using IONOS VirtIO Network Driver Settings Update Scripts (recommended)
The best way to update network configuration is by using IONOS VirtIO Network Driver Settings Update Scripts.
The scripts are distributed in the following versions:
Installer, available for download here: https://github.com/ionos-enterprise/ionos-network-helper/blob/master/WinNet-v0.1.171.0001.exe
Installer will extract the scripts to the user-specified folder and optionally run the scripts.
ZIP archive, available for download here: https://github.com/ionos-enterprise/ionos-network-helper/blob/master/WinNet-v0.1.171.0001.zip
When using the ZIP archive, or not selecting script execution in the installer, scripts can be started manually by launching the update.cmd file in the root folder of the extracted scripts.
If Windows does not allow you to start the installer or update.cmd from the File Explorer window, please launch it directly from the command line.
Offline update using IONOS Windows VirtIO Drivers ISO Image (alternative)
Alternatively, use the VirtIO drivers ISO for Microsoft operating systems provided by IONOS.
1.Use DCD or API to add an ISO image to the virtual server you’d like to update (In DCD select the VM -> Inspector -> Storage -> CD-ROM -> IONOS-Images -> Windows-VirtIO-Drivers).
2.Set the boot flag to the virtual CD/DVD drive with the ISO image.
3.Boot your virtual server from the Windows VirtIO drivers ISO.
4.Open the remote console of the virtual machine.
5.Select an operating system from the list of supported versions. Driver installation or update will be performed automatically.
6.Remove the ISO and restart the VM through the DCD. Make sure that the boot flag is set correctly again.
Manual update
Updating drivers
1.Make sure you have the latest “VirtIO Ethernet Adapter” driver package. The driver package is available in the “Drivers” folder of IONOS VirtIO Network Driver Settings Update Scripts as described above.
2.Open Device Manager.
in the “File Explorer“ window right-click “My PC”, select “Properties” and then “Device Manager”.
3.Under Network Adapters, for each "Red Hat VirtIO Ethernet Adapter":
1.Right-click the adapter and select “Update driver”
2.Select “Browse my computer for driver software”
3.Click “Browse” and select the folder with the driver package suitable for your OS version
4.Click OK and follow the instructions to install the driver.
Updating existing VirtIO network devices
1.Open Device Manager
In the File Explorer window, right-click My PC, select Properties, and then Device Manager
2.Under Network adapters, for each "Red Hat VirtIO Ethernet Adapter":
1.Open Properties (double-click usually works)
2.Go to Advanced tab
3.Navigate and set the following settings there:
"Init.MTUSize"="1500"
"IPv4 Checksum Offload"="Rx & Tx Enabled"
"Large Send Offload V2 (IPv4)"="Enabled"
"Large Send Offload V2 (IPv6)"="Enabled"
"Offload.Rx.Checksum"="All"
"Offload.Tx.Checksum"="All"
"Offload.Tx.LSO"="Maximal"
"TCP Checksum Offload (IPv4)"="Rx & Tx Enabled"
"TCP Checksum Offload (IPv6)"="Rx & Tx Enabled"
"UDP Checksum Offload (IPv4)"="Rx & Tx Enabled"
"UDP Checksum Offload (IPv6)"="Rx & Tx Enabled"
Please be aware that these settings will revert to old Registry values unless the full update procedure is executed as described above.
How can I configure VirtIO settings in Linux?
Please use the configuration below to ensure the stability and performance of the network connections on the operating system side.
Verifying current network configuration
Please make sure to use the MTU setting of 1500 for all network interfaces.
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[email protected]:~# ip link
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...
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2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000
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	link/ether 02:01:26:cb:fc:d5 brd ff:ff:ff:ff:ff:ff
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3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000
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	link/ether 02:01:fb:20:f1:65 brd ff:ff:ff:ff:ff:ff
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4: eth2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000
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	link/ether 02:01:2a:a0:e1:53 brd ff:ff:ff:ff:ff:ff
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Make sure that all of your network interfaces have hardware offloads enabled. This can be done with the ethtool utility; to install ethtool:
For .deb-based distributions:
apt-get install ethtool -y
For .rpm-based distributions:
yum install ethtool.x86_64 -y
Once installed, please do the following for each of your VirtIO-net devices:
Replace the [device_name] with the name of your device, e.g. eth0 or ens0, and check that the highlighted offloads are in the On state:
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[email protected]:~# ethtool -k [device_name]
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...
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tx-checksumming: on
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...
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tx-checksum-ip-generic: on
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...
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...
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tcp-segmentation-offload: on
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tx-tcp-segmentation: on
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tx-tcp-ecn-segmentation: on
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...
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tx-tcp6-segmentation: on
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If you changed any configuration parameters, such as increase MTU or disable offloads for network adapters, please make sure to roll back these changes.
Fixing persistent network interface configuration
Fixing persistent network interface configuration may include removing such configuration in the below files:
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/etc/network/interfaces
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iface eth0 inet static
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...
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pre-up /sbin/ifconfig $IFACE mtu 64000 <-- WRONG
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/etc/dhcp/dhclient.conf (for .deb-based distributions)
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interface "eth0" {
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supersede interface-mtu 64000; <-- WRONG
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}
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/etc/dhcp/dhclient-*.conf (for .rpm based distributions)
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supersede interface-mtu 1500; <-- Correct
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and then restarting the affected network interfaces with ifdown eth0; ifup eth0
Dynamic adjustment of the MTU and offload configuration
In all examples below, please replace the [device_name] with the name of the network device being adjusted, e.g. “eth0” or “ens6”.
Dynamically adjust network device MTU configuration:
ip link set mtu 1500 dev [device_name]
Dynamically enable hardware offloads for VirtIO-net devices. This can be done with the ethtool utility; to install ethtool:
For .deb-based distributions:
apt-get install ethtool -y
For .rpm-based distributions:
yum install ethtool.x86_64 -y
Once installed, please do the following for each of your VirtIO-net devices:
ethtool -K [device_name] tx on tso on