9 Advanced topics 9.10.5 Enabling DNS proxy in NAT mode The NAT engine by default offers the same DNS servers to the guest that are configured on the host. In some scenarios, it can be desirable to hide the DNS server IPs from the guest, for example when this information can change on the host due to expiring DHCP leases. In this case, you can tell the NAT engine to act as DNS proxy using the following command: VBoxManage modifyvm "VM name" --natdnsproxy1 on 9.10.6 Using the host’s resolver as a DNS proxy in NAT mode For resolving network names, the DHCP server of the NAT engine offers a list of registered DNS servers of the host. If for some reason you need to hide this DNS server list and use the host’s resolver settings, thereby forcing the VirtualBox NAT engine to intercept DNS requests and forward them to host’s resolver, use the following command: VBoxManage modifyvm "VM name" --natdnshostresolver1 on Note that this setting is similar to the DNS proxy mode, however whereas the proxy mode just forwards DNS requests to the appropriate servers, the resolver mode will interpret the DNS requests and use the host’s DNS API to query the information and return it to the guest. 9.10.7 Configuring aliasing of the NAT engine By default, the NAT core uses aliasing and uses random ports when generating an alias for a connection. This works well for the most protocols like SSH, FTP and so on. Though some protocols might need a more transparent behavior or may depend on the real port number the packet was sent from. It is possible to change the NAT mode via the VBoxManage frontend with the following commands: VBoxManage modifyvm "VM name" --nataliasmode proxyonly and VBoxManage modifyvm "Linux Guest" --nataliasmode sameports The first example disables aliasing and switches NAT into transparent mode, the second exam- ple enforces preserving of port values. These modes can be combined if necessary. 9.11 Configuring the BIOS DMI information The DMI data VirtualBox provides to guests can be changed for a specific VM. Use the following commands to configure the DMI BIOS information: VBoxManage setextradata "VM name" "VBoxInternal/Devices/pcbios/0/Config/DmiBIOSVendor" "BIOS Vendor" VBoxManage setextradata "VM name" "VBoxInternal/Devices/pcbios/0/Config/DmiBIOSVersion" "BIOS Version" VBoxManage setextradata "VM name" "VBoxInternal/Devices/pcbios/0/Config/DmiBIOSReleaseDate" "BIOS Release Date" VBoxManage setextradata "VM name" "VBoxInternal/Devices/pcbios/0/Config/DmiBIOSReleaseMajor" 1 VBoxManage setextradata "VM name" "VBoxInternal/Devices/pcbios/0/Config/DmiBIOSReleaseMinor" 2 VBoxManage setextradata "VM name" "VBoxInternal/Devices/pcbios/0/Config/DmiBIOSFirmwareMajor" 3 VBoxManage setextradata "VM name" "VBoxInternal/Devices/pcbios/0/Config/DmiBIOSFirmwareMinor" 4 VBoxManage setextradata "VM name" 147