---
layout: doc
title: Networking
permalink: /doc/networking/
redirect_from:
- /doc/qubes-net/
- /en/doc/qubes-net/
- /doc/QubesNet/
- /wiki/QubesNet/
---

VM network in Qubes
===================

Overall description
-------------------

In Qubes, the standard Xen networking is used, based on backend driver in the driver domain and frontend drivers in VMs. In order to eliminate layer 2 attacks originating from a compromised VM, routed networking is used instead of the default bridging of `vif` devices. The default *vif-route* script had some deficiencies (requires `eth0` device to be up, and sets some redundant iptables rules), therefore the custom *vif-route-qubes* script is used.

The IP address of `eth0` interface in AppVM, as well as two IP addresses to be used as nameservers (`DNS1` and `DNS2`), are passed via xenstore to AppVM during its boot (thus, there is no need for DHCP daemon in the network driver domain). `DNS1` and `DNS2` are private addresses; whenever an interface is brought up in the network driver domain, the */usr/lib/qubes/qubes\_setup\_dnat\_to\_ns* script sets up the DNAT iptables rules translating `DNS1` and `DNS2` to the newly learned real dns servers. This way AppVM networking configuration does not need to be changed when configuration in the network driver domain changes (e.g. user switches to a different WLAN). Moreover, in the network driver domain, there is no DNS server either, and consequently there are no ports open to the VMs.

Routing tables examples
-----------------------

VM routing table is simple:

||
|Destination|Gateway|Genmask|Flags|Metric|Ref|Use|Iface|
|0.0.0.0|0.0.0.0|0.0.0.0|U|0|0|0|eth0|

Network driver domain routing table is a bit longer:

||
|Destination|Gateway|Genmask|Flags|Metric|Ref|Use|Iface|
|10.2.0.16|0.0.0.0|255.255.255.255|UH|0|0|0|vif4.0|
|10.2.0.7|0.0.0.0|255.255.255.255|UH|0|0|0|vif10.0|
|10.2.0.9|0.0.0.0|255.255.255.255|UH|0|0|0|vif9.0|
|10.2.0.8|0.0.0.0|255.255.255.255|UH|0|0|0|vif8.0|
|10.2.0.12|0.0.0.0|255.255.255.255|UH|0|0|0|vif3.0|
|192.168.0.0|0.0.0.0|255.255.255.0|U|1|0|0|eth0|
|0.0.0.0|192.168.0.1|0.0.0.0|UG|0|0|0|eth0|