Network Configuration
---------------------
include::attributes.txt[]

{pve} uses a bridged networking model. Each host can have up to 4094
bridges. Bridges are like physical network switches implemented in
software. All VMs can share a single bridge, as if
virtual network cables from each guest were all plugged into the same
switch. But you can also create multiple bridges to separate network
domains.

For connecting VMs to the outside world, bridges are attached to
physical network cards. 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.

Debian traditionally uses the `ifup` and `ifdown` commands to
configure the network. The file `/etc/network/interfaces` contains the
whole network setup. Please refer to to manual page (`man interfaces`)
for a complete format description.

NOTE: {pve} 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.

It is worth mentioning that you can directly edit the configuration
file. All {pve} tools tries hard to keep such direct user
modifications. Using the GUI is still preferable, because it
protect you from errors.


Naming Conventions
~~~~~~~~~~~~~~~~~~

We currently use the following naming conventions for device names:

* Ethernet devices: eth[N], where 0 ≤ N (`eth0`, `eth1`, ...)

* 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 (`eth0.50`, `bond1.30`)

This makes it easier to debug networks problems, because the device
names implies the device type.

Default Configuration using a Bridge
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The installation program creates a single bridge named `vmbr0`, which
is connected to the first ethernet card `eth0`. The corresponding
configuration in `/etc/network/interfaces` looks like this:

----
auto lo
iface lo inet loopback

iface eth0 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 eth0
        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.

A common scenario is that you have a public IP (assume `192.168.10.2`
for this example), and an additional IP block for your VMs
(`10.10.10.1/255.255.255.0`). We recommend the following setup for such
situations:

----
auto lo
iface lo inet loopback

auto eth0
iface eth0 inet static
        address  192.168.10.2
        netmask  255.255.255.0
        gateway  192.168.10.1
        post-up echo 1 > /proc/sys/net/ipv4/conf/eth0/proxy_arp


auto vmbr0
iface vmbr0 inet static
        address  10.10.10.1
        netmask  255.255.255.0
        bridge_ports none
        bridge_stp off
        bridge_fd 0
----


Masquerading (NAT) with `iptables`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

In some cases you may want to use private IPs behind your Proxmox
host's true IP, and masquerade the traffic using NAT:

----
auto lo
iface lo inet loopback

auto eth0
#real IP adress 
iface eth0 inet static
        address  192.168.10.2
        netmask  255.255.255.0
        gateway  192.168.10.1

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 eth0 -j MASQUERADE
        post-down iptables -t nat -D POSTROUTING -s '10.10.10.0/24' -o eth0 -j MASQUERADE
----

////
TODO: explain IPv6 support?
TODO: explan OVS
////
