Network Configuration

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Network 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.

Once the network is configured, you can use the Debian traditional tools ifup and ifdown commands to bring interfaces up and down.

Note Proxmox VE does not write changes directly to /etc/network/interfaces. Instead, we write into a temporary file called /etc/network/interfaces.new, and commit those changes when you reboot the node.

Naming Conventions

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

default-network-setup-bridge.svg

Bridges are like physical network switches implemented in software. All VMs 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
        netmask 255.255.255.0
        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.

Routed Configuration

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.

Tip Some providers allows you to register additional MACs on there management interface. This avoids the problem, but is 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.

default-network-setup-routed.svg

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 (203.0.113.16/29). We recommend the following setup for such situations:

auto lo
iface lo inet loopback

auto eno1
iface eno1 inet static
        address  198.51.100.5
        netmask  255.255.255.0
        gateway  198.51.100.1
        post-up echo 1 > /proc/sys/net/ipv4/ip_forward
        post-up echo 1 > /proc/sys/net/ipv4/conf/eno1/proxy_arp


auto vmbr0
iface vmbr0 inet static
        address  203.0.113.17
        netmask  255.255.255.248
        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
        netmask  255.255.255.0
        gateway  198.51.100.1

auto vmbr0
#private sub network
iface vmbr0 inet static
        address  10.10.10.1
        netmask  255.255.255.0
        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

Linux Bond

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 active-backup mode.
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.

Example: Use bond with fixed IP address
auto lo
iface lo inet loopback

iface eno1 inet manual

iface eno2 inet manual

auto bond0
iface bond0 inet static
      slaves eno1 eno2
      address  192.168.1.2
      netmask  255.255.255.0
      bond_miimon 100
      bond_mode 802.3ad
      bond_xmit_hash_policy layer2+3

auto vmbr0
iface vmbr0 inet static
        address  10.10.10.2
        netmask  255.255.255.0
        gateway  10.10.10.1
        bridge_ports eno1
        bridge_stp off
        bridge_fd 0
default-network-setup-bond.svg

Another possibility it to use the bond directly as bridge port. This can be used to make the guest network fault-tolerant.

Example: Use a bond as bridge port
auto lo
iface lo inet loopback

iface eno1 inet manual

iface eno2 inet manual

auto bond0
iface bond0 inet manual
      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
        netmask  255.255.255.0
        gateway  10.10.10.1
        bridge_ports bond0
        bridge_stp off
        bridge_fd 0

VLAN 802.1Q

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 confinuration. The networking layer supports differnet 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 the 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, if e.g. in our default network, a guest VLAN 5 is used to create eno1.5 and vmbr0v5, which remains until rebooting.

  • 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.

Example: Use VLAN 5 for the Proxmox VE management IP with traditional Linux bridge
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
        netmask  255.255.255.0
        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
Example: Use VLAN 5 for the Proxmox VE management IP with VLAN aware Linux bridge
auto lo
iface lo inet loopback

iface eno1 inet manual


auto vmbr0.5
iface vmbr0.5 inet static
        address  10.10.10.2
        netmask  255.255.255.0
        gateway  10.10.10.1

auto vmbr0
iface vmbr0 inet manual
        bridge_ports eno1
        bridge_stp off
        bridge_fd 0
        bridge_vlan_aware yes

The next example is the same setup but a bond is used to make this network fail-safe.

Example: Use VLAN 5 with bond0 for the Proxmox VE management IP with traditional Linux bridge
auto lo
iface lo inet loopback

iface eno1 inet manual

iface eno2 inet manual

auto bond0
iface bond0 inet manual
      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
        netmask  255.255.255.0
        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