Sun Microsystems VIRTUALBOX VERSION 3.1.0_BETA2 - Manual (Page 91)

6 Virtual networking
use the same ports on the guest and on the host). You can use any ports on the host
which are not already in use by a service. An example of how to set up incoming NAT
connections to an ssh server on the guest requires the following three commands:
VBoxManage setextradata "Linux Guest"
"VBoxInternal/Devices/pcnet/0/LUN#0/Config/guestssh/Protocol" TCP
VBoxManage setextradata "Linux Guest"
"VBoxInternal/Devices/pcnet/0/LUN#0/Config/guestssh/GuestPort" 22
VBoxManage setextradata "Linux Guest"
"VBoxInternal/Devices/pcnet/0/LUN#0/Config/guestssh/HostPort" 2222
The above example assumes a PCNet virtual network card; if you have configured
the guest to use the Intel PRO/1000, replace “pcnet” with “e1000” in the above com-
mands. Similarly, if you want to configure a different interface instance replace the
/0/
with the appropriate index. pcnet and e1000 are counted separately in this
respect, and counting starts at 0 for both types.
The name guestssh is an arbitrary one chosen for this particular forwarding con-
figuration. With that configuration in place, all TCP connections to port 2222 on the
host will be forwarded to port 22 on the guest. Protocol can be either of TCP or UDP
(these are case insensitive). To remove a mapping again, use the same commands, but
leaving out the values (in this case TCP, 22 and 2222).
It is not possible to configure incoming NAT connections while the VM is running.
However you can change the settings for a VM which is currently saved (or powered
off at a snapshot).
6.3.2 PXE booting with NAT
PXE booting is now supported in NAT mode. The NAT DHCP server provides a boot
file name of the form vmname.pxe if the directory TFTP exists in the directory where
the user’s VirtualBox.xml file is kept. It is the responsibility of the user to provide
vmname.pxe
.
6.3.3 NAT limitations
There are four limitations of NAT mode which users should be aware of:
ICMP protocol limitations: Some frequently used network debugging tools (e.g.
ping or tracerouting) rely on the ICMP protocol for sending/receiving messages.
While ICMP support has been improved with VirtualBox 2.1 (ping should now
work), some other tools may not work reliably.
Receiving of UDP broadcasts is not reliable: The guest does not reliably receive
broadcasts, since, in order to save resources, it only listens for a certain amount
of time after the guest has sent UDP data on a particular port. As a consequence,
NetBios name resolution based on broadcasts does not always work (but WINS
always works). As a workaround, you can use the numeric IP of the desired
server in the \\server\share notation.
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