16.3. Recommended virtual machine networking configurations
In many scenarios, the default VM networking configuration is sufficient. However, if adjusting the configuration is required, you can use the command-line interface (CLI) or the RHEL 9 web console to do so. The following sections describe selected VM network setups for such situations.
16.3.1. Configuring externally visible virtual machines using the command-line interface
By default, a newly created VM connects to a NAT-type network that uses virbr0, the default virtual bridge on the host. This ensures that the VM can use the host’s network interface controller (NIC) for connecting to outside networks, but the VM is not reachable from external systems.
If you require a VM to appear on the same external network as the hypervisor, you must use bridged mode instead. To do so, attach the VM to a bridge device connected to the hypervisor’s physical network device. To use the command-line interface for this, follow the instructions below.
Conditions préalables
- A shut-down existing VM with the default NAT setup.
The IP configuration of the hypervisor. This varies depending on the network connection of the host. As an example, this procedure uses a scenario where the host is connected to the network using an ethernet cable, and the hosts' physical NIC MAC address is assigned to a static IP on a DHCP server. Therefore, the ethernet interface is treated as the hypervisor IP.
To obtain the IP configuration of the ethernet interface, use the
ip addrutility:# ip addr [...] enp0s25: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether 54:ee:75:49:dc:46 brd ff:ff:ff:ff:ff:ff inet 10.0.0.148/24 brd 10.0.0.255 scope global dynamic noprefixroute enp0s25
Procédure
Create and set up a bridge connection for the physical interface on the host. For instructions, see the Configuring a network bridge.
Note that in a scenario where static IP assignment is used, you must move the IPv4 setting of the physical ethernet interface to the bridge interface.
Modify the VM’s network to use the created bridged interface. For example, the following sets testguest to use bridge0.
# virt-xml testguest --edit --network bridge=bridge0 Domain 'testguest' defined successfully.Start the VM.
# virsh start testguestIn the guest operating system, adjust the IP and DHCP settings of the system’s network interface as if the VM was another physical system in the same network as the hypervisor.
The specific steps for this will differ depending on the guest OS used by the VM. For example, if the guest OS is RHEL 9, see Configuring an Ethernet connection.
Vérification
Ensure the newly created bridge is running and contains both the host’s physical interface and the interface of the VM.
# ip link show master bridge0 2: enp0s25: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel master bridge0 state UP mode DEFAULT group default qlen 1000 link/ether 54:ee:75:49:dc:46 brd ff:ff:ff:ff:ff:ff 10: vnet0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel master bridge0 state UNKNOWN mode DEFAULT group default qlen 1000 link/ether fe:54:00:89:15:40 brd ff:ff:ff:ff:ff:ffEnsure the VM appears on the same external network as the hypervisor:
In the guest operating system, obtain the network ID of the system. For example, if it is a Linux guest:
# ip addr [...] enp0s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether 52:54:00:09:15:46 brd ff:ff:ff:ff:ff:ff inet 10.0.0.150/24 brd 10.0.0.255 scope global dynamic noprefixroute enp0s0From an external system connected to the local network, connect to the VM using the obtained ID.
# ssh root@10.0.0.150 root@10.0.0.150's password: Last login: Mon Sep 24 12:05:36 2019 root~#*If the connection works, the network has been configured successfully.
Résolution de problèmes
In certain situations, such as when using a client-to-site VPN while the VM is hosted on the client, using bridged mode for making your VMs available to external locations is not possible.
To work around this problem, you can set destination NAT using
nftablesfor the VM.
Ressources supplémentaires
16.3.2. Configuring externally visible virtual machines using the web console
By default, a newly created VM connects to a NAT-type network that uses virbr0, the default virtual bridge on the host. This ensures that the VM can use the host’s network interface controller (NIC) for connecting to outside networks, but the VM is not reachable from external systems.
If you require a VM to appear on the same external network as the hypervisor, you must use bridged mode instead. To do so, attach the VM to a bridge device connected to the hypervisor’s physical network device. To use the RHEL 9 web console for this, follow the instructions below.
Conditions préalables
- The web console VM plug-in is installed on your system.
- A shut-down existing VM with the default NAT setup.
The IP configuration of the hypervisor. This varies depending on the network connection of the host. As an example, this procedure uses a scenario where the host is connected to the network using an ethernet cable, and the hosts' physical NIC MAC address is assigned to a static IP on a DHCP server. Therefore, the ethernet interface is treated as the hypervisor IP.
To obtain the IP configuration of the ethernet interface, go to the
Networkingtab in the web console, and see theInterfacessection.Procédure
Create and set up a bridge connection for the physical interface on the host. For instructions, see Configuring network bridges in the web console.
Note that in a scenario where static IP assignment is used, you must move the IPv4 setting of the physical ethernet interface to the bridge interface.
Modify the VM’s network to use the bridged interface. In the Network Interfaces tab of the VM:
- Click Add Network Interface
In the
Add Virtual Network Interfacedialog, set:-
Interface Type to
Bridge to LAN -
Source to the newly created bridge, for example
bridge0
-
Interface Type to
- Click Add
- Optional: Click Unplug for all the other interfaces connected to the VM.
- Click Run to start the VM.
In the guest operating system, adjust the IP and DHCP settings of the system’s network interface as if the VM was another physical system in the same network as the hypervisor.
The specific steps for this will differ depending on the guest OS used by the VM. For example, if the guest OS is RHEL 9, see Configuring an Ethernet connection.
Vérification
- In the Networking tab of the host’s web console, click the row with the newly created bridge to ensure it is running and contains both the host’s physical interface and the interface of the VM.
Ensure the VM appears on the same external network as the hypervisor.
In the guest operating system, obtain the network ID of the system. For example, if it is a Linux guest:
# ip addr [...] enp0s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether 52:54:00:09:15:46 brd ff:ff:ff:ff:ff:ff inet 10.0.0.150/24 brd 10.0.0.255 scope global dynamic noprefixroute enp0s0From an external system connected to the local network, connect to the VM using the obtained ID.
# ssh root@10.0.0.150 root@110.34.5.18's password: Last login: Mon Sep 24 12:05:36 2019 root~#*If the connection works, the network has been configured successfully.
Résolution de problèmes
- In certain situations, such as when using a client-to-site VPN while the VM is hosted on the client, using bridged mode for making your VMs available to external locations is not possible.