This document describes common errors that you may run into when using nestedvirtualization and methods for resolving those errors. For more informationabout nested virtualization, seeCreating nested VMs.

Can't start nested VM

If your project is part of an organization, your organization might havedisabled the ability to create VMs with nested virtualization. Make sure thatnested virtualization is allowed before you try to create a VM that hasnested virtualization enabled.

Processor not displaying nested virtualization

If thegrep -c vmx /proc/cpuinfo command returns0 and reports that the VMis not enabled for nesting, make sure that you have started your VM with a CPUplatform of Haswell or later. For more information, seeNested virtualizationoverview.

Can't exit nested VM

If you did not runscreen before each nested VM session, you can eithershut down the nested VM or stop the process from another terminal. To shut downthe nested VM, run thepoweroff command from within your nested VM.Alternatively, log into the host VM in another terminal and end the process,then runscreen on the host VM before you start a new nested VM.

iptables not forwarding traffic

• iptables resolve rules from top to bottom. Make sure your rules are higherpriority than other rules.
• Check that there are no conflicting rules intercepting your packets.

• Consider flushing youriptables:

  Note: Flushingiptables disables your firewall. You should only do this ifyou want to start over configuring your firewall.

  1. First, set the default policies:

     sudo iptables -P INPUT ACCEPTsudo iptables -P FORWARD ACCEPTsudo iptables -P OUTPUT ACCEPT

  2. Next, flush all tables and chains, and delete non-default chains:

     sudo iptables -t nat -Fsudo iptables -t mangle -Fsudo iptables -Fsudo iptables -X