Specifications

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VMware GSX Server Virtual Machine Guide
When data arrives from the external network for the virtual machine on the private
network, the NAT device receives the data, replaces the network address with that of
the virtual machine and forwards the data to the virtual machine on the virtual
network. This translation occurs automatically and requires minimal configuration on
the guest and the host.
The Host Computer and the NAT Network
The host computer has a host virtual adapter on the NAT network (identical to the
host virtual adapter on the host-only network). This adapter allows the host and the
virtual machines to communicate with each other for such purposes as file sharing.
The NAT never forwards traffic from the host virtual adapter.
DHCP on the NAT Network
In order to make networking configuration easy, a DHCP server is automatically
installed when you install GSX Server. Virtual machines running on the network with
the NAT device can dynamically obtain their IP addresses by sending out DHCP
requests. The DHCP server on the NAT network, which is also used in host-only
networking configurations, dynamically allocates IP addresses in the range of
<net>.128 through <net>.254, where <net> is the network number assigned to your
NAT network. GSX Server always uses a Class C address for NAT networks. IP addresses
<net>.3 through <net>.127 can be used for static IP addresses. IP address <net>.1 is
reserved for the host adapter; <net>.2 is reserved for the NAT device.
In addition to the IP address, the DHCP server on the NAT network also sends out
additional configuration information that enables the virtual machine to operate
automatically. This information includes the default gateway and the DNS server. In
the DHCP response, the NAT device instructs the virtual machine to use the IP address
<net>.2 as the default gateway and DNS server. This causes all IP packets destined for
the external network and DNS requests to be forwarded to the NAT device.
DNS on the NAT Network
The NAT device acts as a DNS server for the virtual machines on the NAT network.
Actually, the NAT device is a DNS proxy and merely forwards DNS requests from the
virtual machines to a DNS server that is known by the host. Responses come back to
the NAT device, which then forwards them to the virtual machines.
If they get their configuration information from DHCP, the virtual machines on the NAT
network automatically use the NAT device as the DNS server. However, the virtual
machines can be statically configured to use another DNS server.