Creating a DNS Record for a Host with Two or More IP Addresses (168321)


The information in this article applies to:

  • Microsoft Windows NT Server 4.0
This article was previously published under Q168321

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.
Modification Type:MajorLast Reviewed:8/9/2001
Keywords:kbnetwork KB168321
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