Introduction to Windows Networking - MCTS Guide to Microsoft Windows Server 2008 Active Directory Configuration - page 332

• The computer is connected to a physical network that hosts multiple IP networks. This sit-
uation can occur if your network addressing scheme is transitioning from one network ID
to another, and you need a server to be available to both the old and the new IP addresses
until the transition is completed. It can also occur when you have multiple groups of com-
puters (or hosts and virtual machines) connected to the same physical network but with
different network addresses. If all the computers need access to server resources, the
servers can be configured with IP addresses to serve all the IP networks.

Figure 8-7

The Advanced TCP/IP Settings dialog box

When multiple IP addresses are assigned to a Windows computer that
uses a Windows DNS server supporting dynamic DNS (the default DNS
server configuration), the DNS server has a host entry for each IP address
assigned to the computer.

Configuring the Default Gateway Almost all IP address configurations require a
default gateway address. The default gateway, which is usually a router or a computer config-
ured to act as a router, tells the computer where packets destined for another network should be
sent. By definition, the default gateway's address must have the same network ID as the host's
network ID.
You can configure multiple default gateways in the Advanced TCP/IP Settings dialog box, and
then Windows attempts to select the gateway with the best metric automatically. The metric is a
value assigned to the gateway based on the speed of the interface used to access the gateway.
Multiple gateways provide fault tolerance to a computer, so if the primary default gateway is no
longer responding, Windows switches to another gateway. By using a new feature in Windows
Server 2008 and Vista called fail-back, Windows attempts periodically to communicate with the
original default gateway. If the original gateway comes back online, Windows switches back to it.
Using Multihomed Servers A multihomed server has two or more NICs, each attached
to a different IP network. Each NIC is assigned a network connection and requires its own