Proxmox VE is using the Linux network stack. This provides a lot of flexibility on how to set up the network on the Proxmox VE nodes. The configuration can be done either via the GUI, or by manually editing the file /etc/network/interfaces, which contains the whole network configuration. The interfaces(5) manual page contains the complete format description. All Proxmox VE tools try hard to keep direct user modifications, but using the GUI is still preferable, because it protects you from errors.
A vmbr interface is needed to connect guests to the underlying physical network. They are a Linux bridge which can be thought of as a virtual switch to which the guests and physical interfaces are connected to. This section provides some examples on how the network can be set up to accomodate different use cases like redundancy with a bond, vlans or routed and NAT setups.
The Software Defined Network is an option for more complex virtual networks in Proxmox VE clusters.
|It’s discouraged to use the traditional Debian tools ifup and ifdown if unsure, as they have some pitfalls like interupting all guest traffic on ifdown vmbrX but not reconnecting those guest again when doing ifup on the same bridge later.|
Apply Network Changes
Proxmox VE does not write changes directly to /etc/network/interfaces. Instead, we write into a temporary file called /etc/network/interfaces.new, this way you can do many related changes at once. This also allows to ensure your changes are correct before applying, as a wrong network configuration may render a node inaccessible.
Live-Reload Network with ifupdown2
With the recommended ifupdown2 package (default for new installations since Proxmox VE 7.0), it is possible to apply network configuration changes without a reboot. If you change the network configuration via the GUI, you can click the Apply Configuration button. This will move changes from the staging interfaces.new file to /etc/network/interfaces and apply them live.
If you made manual changes directly to the /etc/network/interfaces file, you can apply them by running ifreload -a
|If you installed Proxmox VE on top of Debian, or upgraded to Proxmox VE 7.0 from an older Proxmox VE installation, make sure ifupdown2 is installed: apt install ifupdown2|
Reboot Node to Apply
Another way to apply a new network configuration is to reboot the node. In that case the systemd service pvenetcommit will activate the staging interfaces.new file before the networking service will apply that configuration.
We currently use the following naming conventions for device names:
Ethernet devices: en*, systemd network interface names. This naming scheme is used for new Proxmox VE installations since version 5.0.
Ethernet devices: eth[N], where 0 ≤ N (eth0, eth1, …) This naming scheme is used for Proxmox VE hosts which were installed before the 5.0 release. When upgrading to 5.0, the names are kept as-is.
Bridge names: vmbr[N], where 0 ≤ N ≤ 4094 (vmbr0 - vmbr4094)
Bonds: bond[N], where 0 ≤ N (bond0, bond1, …)
VLANs: Simply add the VLAN number to the device name, separated by a period (eno1.50, bond1.30)
This makes it easier to debug networks problems, because the device name implies the device type.
Systemd Network Interface Names
Systemd uses the two character prefix en for Ethernet network devices. The next characters depends on the device driver and the fact which schema matches first.
o<index>[n<phys_port_name>|d<dev_port>] — devices on board
s<slot>[f<function>][n<phys_port_name>|d<dev_port>] — device by hotplug id
[P<domain>]p<bus>s<slot>[f<function>][n<phys_port_name>|d<dev_port>] — devices by bus id
x<MAC> — device by MAC address
The most common patterns are:
eno1 — is the first on board NIC
enp3s0f1 — is the NIC on pcibus 3 slot 0 and use the NIC function 1.
For more information see Predictable Network Interface Names.
Choosing a network configuration
Depending on your current network organization and your resources you can choose either a bridged, routed, or masquerading networking setup.
Proxmox VE server in a private LAN, using an external gateway to reach the internet
The Bridged model makes the most sense in this case, and this is also the default mode on new Proxmox VE installations. Each of your Guest system will have a virtual interface attached to the Proxmox VE bridge. This is similar in effect to having the Guest network card directly connected to a new switch on your LAN, the Proxmox VE host playing the role of the switch.
Proxmox VE server at hosting provider, with public IP ranges for Guests
For this setup, you can use either a Bridged or Routed model, depending on what your provider allows.
Proxmox VE server at hosting provider, with a single public IP address
In that case the only way to get outgoing network accesses for your guest systems is to use Masquerading. For incoming network access to your guests, you will need to configure Port Forwarding.
For further flexibility, you can configure VLANs (IEEE 802.1q) and network bonding, also known as "link aggregation". That way it is possible to build complex and flexible virtual networks.
Default Configuration using a Bridge
Bridges are like physical network switches implemented in software. All virtual guests can share a single bridge, or you can create multiple bridges to separate network domains. Each host can have up to 4094 bridges.
The installation program creates a single bridge named vmbr0, which is connected to the first Ethernet card. The corresponding configuration in /etc/network/interfaces might look like this:
auto lo iface lo inet loopback iface eno1 inet manual auto vmbr0 iface vmbr0 inet static address 192.168.10.2/24 gateway 192.168.10.1 bridge-ports eno1 bridge-stp off bridge-fd 0
Virtual machines behave as if they were directly connected to the physical network. The network, in turn, sees each virtual machine as having its own MAC, even though there is only one network cable connecting all of these VMs to the network.
Most hosting providers do not support the above setup. For security reasons, they disable networking as soon as they detect multiple MAC addresses on a single interface.
|Some providers allow you to register additional MACs through their management interface. This avoids the problem, but can be clumsy to configure because you need to register a MAC for each of your VMs.|
You can avoid the problem by “routing” all traffic via a single interface. This makes sure that all network packets use the same MAC address.
A common scenario is that you have a public IP (assume 198.51.100.5 for this example), and an additional IP block for your VMs (203.0.113.16/28). We recommend the following setup for such situations:
auto lo iface lo inet loopback auto eno0 iface eno0 inet static address 198.51.100.5/29 gateway 198.51.100.1 post-up echo 1 > /proc/sys/net/ipv4/ip_forward post-up echo 1 > /proc/sys/net/ipv4/conf/eno0/proxy_arp auto vmbr0 iface vmbr0 inet static address 203.0.113.17/28 bridge-ports none bridge-stp off bridge-fd 0
Masquerading (NAT) with iptables
Masquerading allows guests having only a private IP address to access the network by using the host IP address for outgoing traffic. Each outgoing packet is rewritten by iptables to appear as originating from the host, and responses are rewritten accordingly to be routed to the original sender.
auto lo iface lo inet loopback auto eno1 #real IP address iface eno1 inet static address 198.51.100.5/24 gateway 198.51.100.1 auto vmbr0 #private sub network iface vmbr0 inet static address 10.10.10.1/24 bridge-ports none bridge-stp off bridge-fd 0 post-up echo 1 > /proc/sys/net/ipv4/ip_forward post-up iptables -t nat -A POSTROUTING -s '10.10.10.0/24' -o eno1 -j MASQUERADE post-down iptables -t nat -D POSTROUTING -s '10.10.10.0/24' -o eno1 -j MASQUERADE
|In some masquerade setups with firewall enabled, conntrack zones might be needed for outgoing connections. Otherwise the firewall could block outgoing connections since they will prefer the POSTROUTING of the VM bridge (and not MASQUERADE).|
Adding these lines in the /etc/network/interfaces can fix this problem:
post-up iptables -t raw -I PREROUTING -i fwbr+ -j CT --zone 1 post-down iptables -t raw -D PREROUTING -i fwbr+ -j CT --zone 1
For more information about this, refer to the following links:
Bonding (also called NIC teaming or Link Aggregation) is a technique for binding multiple NIC’s to a single network device. It is possible to achieve different goals, like make the network fault-tolerant, increase the performance or both together.
High-speed hardware like Fibre Channel and the associated switching hardware can be quite expensive. By doing link aggregation, two NICs can appear as one logical interface, resulting in double speed. This is a native Linux kernel feature that is supported by most switches. If your nodes have multiple Ethernet ports, you can distribute your points of failure by running network cables to different switches and the bonded connection will failover to one cable or the other in case of network trouble.
Aggregated links can improve live-migration delays and improve the speed of replication of data between Proxmox VE Cluster nodes.
There are 7 modes for bonding:
Round-robin (balance-rr): Transmit network packets in sequential order from the first available network interface (NIC) slave through the last. This mode provides load balancing and fault tolerance.
Active-backup (active-backup): Only one NIC slave in the bond is active. A different slave becomes active if, and only if, the active slave fails. The single logical bonded interface’s MAC address is externally visible on only one NIC (port) to avoid distortion in the network switch. This mode provides fault tolerance.
XOR (balance-xor): Transmit network packets based on [(source MAC address XOR’d with destination MAC address) modulo NIC slave count]. This selects the same NIC slave for each destination MAC address. This mode provides load balancing and fault tolerance.
Broadcast (broadcast): Transmit network packets on all slave network interfaces. This mode provides fault tolerance.
IEEE 802.3ad Dynamic link aggregation (802.3ad)(LACP): Creates aggregation groups that share the same speed and duplex settings. Utilizes all slave network interfaces in the active aggregator group according to the 802.3ad specification.
Adaptive transmit load balancing (balance-tlb): Linux bonding driver mode that does not require any special network-switch support. The outgoing network packet traffic is distributed according to the current load (computed relative to the speed) on each network interface slave. Incoming traffic is received by one currently designated slave network interface. If this receiving slave fails, another slave takes over the MAC address of the failed receiving slave.
Adaptive load balancing (balance-alb): Includes balance-tlb plus receive load balancing (rlb) for IPV4 traffic, and does not require any special network switch support. The receive load balancing is achieved by ARP negotiation. The bonding driver intercepts the ARP Replies sent by the local system on their way out and overwrites the source hardware address with the unique hardware address of one of the NIC slaves in the single logical bonded interface such that different network-peers use different MAC addresses for their network packet traffic.
If your switch support the LACP (IEEE 802.3ad) protocol then we recommend using
the corresponding bonding mode (802.3ad). Otherwise you should generally use the
If you intend to run your cluster network on the bonding interfaces, then you have to use active-passive mode on the bonding interfaces, other modes are unsupported.
The following bond configuration can be used as distributed/shared storage network. The benefit would be that you get more speed and the network will be fault-tolerant.
auto lo iface lo inet loopback iface eno1 inet manual iface eno2 inet manual iface eno3 inet manual auto bond0 iface bond0 inet static bond-slaves eno1 eno2 address 192.168.1.2/24 bond-miimon 100 bond-mode 802.3ad bond-xmit-hash-policy layer2+3 auto vmbr0 iface vmbr0 inet static address 10.10.10.2/24 gateway 10.10.10.1 bridge-ports eno3 bridge-stp off bridge-fd 0
Another possibility it to use the bond directly as bridge port. This can be used to make the guest network fault-tolerant.
auto lo iface lo inet loopback iface eno1 inet manual iface eno2 inet manual auto bond0 iface bond0 inet manual bond-slaves eno1 eno2 bond-miimon 100 bond-mode 802.3ad bond-xmit-hash-policy layer2+3 auto vmbr0 iface vmbr0 inet static address 10.10.10.2/24 gateway 10.10.10.1 bridge-ports bond0 bridge-stp off bridge-fd 0
A virtual LAN (VLAN) is a broadcast domain that is partitioned and isolated in the network at layer two. So it is possible to have multiple networks (4096) in a physical network, each independent of the other ones.
Each VLAN network is identified by a number often called tag. Network packages are then tagged to identify which virtual network they belong to.
VLAN for Guest Networks
Proxmox VE supports this setup out of the box. You can specify the VLAN tag when you create a VM. The VLAN tag is part of the guest network configuration. The networking layer supports different modes to implement VLANs, depending on the bridge configuration:
VLAN awareness on the Linux bridge: In this case, each guest’s virtual network card is assigned to a VLAN tag, which is transparently supported by the Linux bridge. Trunk mode is also possible, but that makes configuration in the guest necessary.
"traditional" VLAN on the Linux bridge: In contrast to the VLAN awareness method, this method is not transparent and creates a VLAN device with associated bridge for each VLAN. That is, creating a guest on VLAN 5 for example, would create two interfaces eno1.5 and vmbr0v5, which would remain until a reboot occurs.
Open vSwitch VLAN: This mode uses the OVS VLAN feature.
Guest configured VLAN: VLANs are assigned inside the guest. In this case, the setup is completely done inside the guest and can not be influenced from the outside. The benefit is that you can use more than one VLAN on a single virtual NIC.
VLAN on the Host
To allow host communication with an isolated network. It is possible to apply VLAN tags to any network device (NIC, Bond, Bridge). In general, you should configure the VLAN on the interface with the least abstraction layers between itself and the physical NIC.
For example, in a default configuration where you want to place the host management address on a separate VLAN.
auto lo iface lo inet loopback iface eno1 inet manual iface eno1.5 inet manual auto vmbr0v5 iface vmbr0v5 inet static address 10.10.10.2/24 gateway 10.10.10.1 bridge-ports eno1.5 bridge-stp off bridge-fd 0 auto vmbr0 iface vmbr0 inet manual bridge-ports eno1 bridge-stp off bridge-fd 0
auto lo iface lo inet loopback iface eno1 inet manual auto vmbr0.5 iface vmbr0.5 inet static address 10.10.10.2/24 gateway 10.10.10.1 auto vmbr0 iface vmbr0 inet manual bridge-ports eno1 bridge-stp off bridge-fd 0 bridge-vlan-aware yes bridge-vids 2-4094
The next example is the same setup but a bond is used to make this network fail-safe.
auto lo iface lo inet loopback iface eno1 inet manual iface eno2 inet manual auto bond0 iface bond0 inet manual bond-slaves eno1 eno2 bond-miimon 100 bond-mode 802.3ad bond-xmit-hash-policy layer2+3 iface bond0.5 inet manual auto vmbr0v5 iface vmbr0v5 inet static address 10.10.10.2/24 gateway 10.10.10.1 bridge-ports bond0.5 bridge-stp off bridge-fd 0 auto vmbr0 iface vmbr0 inet manual bridge-ports bond0 bridge-stp off bridge-fd 0
Disabling IPv6 on the Node
Proxmox VE works correctly in all environments, irrespective of whether IPv6 is deployed or not. We recommend leaving all settings at the provided defaults.
Should you still need to disable support for IPv6 on your node, do so by creating an appropriate sysctl.conf (5) snippet file and setting the proper sysctls, for example adding /etc/sysctl.d/disable-ipv6.conf with content:
net.ipv6.conf.all.disable_ipv6 = 1 net.ipv6.conf.default.disable_ipv6 = 1
This method is preferred to disabling the loading of the IPv6 module on the kernel commandline.
Disabling MAC Learning on a Bridge
By default, MAC learning is enabled on a bridge to ensure a smooth experience with virtual guests and their networks.
But in some environments this can be undesired. Since Proxmox VE 7.3 you can disable MAC learning on the bridge by setting the ‘bridge-disable-mac-learning 1` configuration on a bridge in `/etc/network/interfaces’, for example:
# ... auto vmbr0 iface vmbr0 inet static address 10.10.10.2/24 gateway 10.10.10.1 bridge-ports ens18 bridge-stp off bridge-fd 0 bridge-disable-mac-learning 1
Once enabled, Proxmox VE will manually add the configured MAC address from VMs and Containers to the bridges forwarding database to ensure that guest can still use the network - but only when they are using their actual MAC address.