DOCUMENT:Q168321  09-AUG-2001  [winnt]
TITLE   :Creating a DNS Record for a Host with Two or More IP Addresses
PRODUCT :Microsoft Windows NT
PROD/VER:winnt:4.0
OPER/SYS:
KEYWORDS:kbnetwork

======================================================================
-------------------------------------------------------------------------------
The information in this article applies to:

 - Microsoft Windows NT Server version 4.0 
-------------------------------------------------------------------------------

SUMMARY
=======

You may have a computer with two or more network interface cards (NICs), or one
NIC with more than one IP address, and need to add a record for the additional
IP address(es) to your Domain Name Service (DNS) server. This article explains
how to add this entry.

MORE INFORMATION
================

An "A" record needs to be created for each IP address that the host uses.

For example, you have a server whose DNS host name is <myserver> and DNS
domain name is <mydomain.com>. This server has 2 IP addresses assigned to
it: IPAddress1 and IPAddress2 (replace IPAddress1 and IPAddress2 with server's
IP addresses).

To add these IP addresses, create 2 A records in the <mydomain.com> zone:

   Myserver   A   <IPAddress1>
   Myserver   A   <IPAddress2>

NOTE: The Microsoft DNS Server supports round robin, which is a technique used as
a form of load balancing between servers (to get more information about this
feature, refer to RFC 1794). This feature will make DNS send both IP addresses
when a query is received for myserver.mydomain.com. The client (or Resolver)
will always use the first one. The next time DNS receives a query for this name
the order of the list of IP addresses is changed in a round robin fashion (the
address that was first in the previous list will be last in the new list). Round
Robin of Cname records is not supported because there should be only one
canonical name for any one alias.

If, for some reason, you need the Resolver to get the same IP address every time,
create two more "A" records assigning a unique name to each address. For
example, you can create:

   Altname1   A   <IPAddress1>
   Altname2   A   <IPAddress2>

Using this method, a Resolver will always obtain IPAddress1 when sending a query
for Altname1 and will always obtain IPAddress2 when sending a query for
Altname2.

NOTE: A "CNAME" record is not used, since DNS will look up the IP address of
<Myserver>, returning the 2 IP addresses.

See RFC 2181 for more information.

Additional query words: DNS multi-homed multiple IP Addresses Multihomed multi homed

======================================================================
Keywords          : kbnetwork 
Technology        : kbWinNTsearch kbWinNT400search kbWinNTSsearch kbWinNTS400search kbWinNTS400
Version           : winnt:4.0

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS
PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND.  MICROSOFT DISCLAIMS
ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  IN NO
EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR
ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL,
CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF
MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES.  SOME STATES DO NOT ALLOW THE EXCLUSION
OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES
SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 2001.