DNS 'Host' Record Appears to Be Missing

[This topic is intended to address a specific issue called out by the Exchange Server Analyzer Tool. You should apply it only to systems that have had the Exchange Server Analyzer Tool run against them and are experiencing that specific issue. The Exchange Server Analyzer Tool, available as a free download, remotely collects configuration data from each server in the topology and automatically analyzes the data. The resulting report details important configuration issues, potential problems, and nondefault product settings. By following these recommendations, you can achieve better performance, scalability, reliability, and uptime. For more information about the tool or to download the latest versions, see "Microsoft Exchange Analyzers" at http://go.microsoft.com/fwlink/?linkid=34707.]  

Topic Last Modified: 2006-04-13

The Microsoft® Exchange Server Analyzer Tool performs a Domain Name System (DNS) lookup on the DNS server to retrieve the Host (A) record of the Exchange server. If the DNS lookup operation does not return an IP address, the Exchange Server Analyzer displays a warning that the Host (A) record appears to be missing.

The DNS lookup of the Host (A) record from the Exchange Server 2003 computer could fail for the following reasons:

  • The DNS server maybe down or not responding because of a network failure or other reasons.

  • The Host (A) record for Exchange Server 2003 could be missing on the DNS server because the record may not be available, may be incorrect, or the DNS server may not be configured to allow dynamic host record updates.

When the DNS server is down, there can be mail routing delays and other service failures.

Exchange Server 2003 relies on host name resolution for both local and external SMTP-based messaging systems in the network. Host name resolution is based primarily on DNS, and DNS is a critical network service. The failure of a DNS server can prevent users from locating your messaging system. Active Directory and the Exchange Server 2003 organization cannot function without DNS. Messaging clients will query DNS to locate internal resources, such as domain controllers and mailbox servers. Exchange Server 2003, on the other hand, relies on DNS to retrieve Internet Protocol (IP) addresses of domain controllers for directory lookups and external Simple Mail Transfer Protocol (SMTP) hosts when Exchange Server 2003sends messages to the Internet.

To fix the issue, verify that the DNS server is running and that the Host (A) record is registered.

To verify that the DNS server is online and that the Host record is present
  1. Verify that the DNS server is running by performing one or more of the following steps:

  2. Use nslookup to verify that the Host (A) record exists on the DNS server. For more information, see "To verify A resource records exist in DNS" (http://go.microsoft.com/fwlink/?LinkId=63001).

  3. If the Host (A) resource record does not exist, manually add or modify the A resource record or configure the DNS server to allow dynamic record updates

For information about Exchange Server 2003 system monitoring, see "System Monitoring with Exchange Server 2003 Management Pack" in the Exchange Server 2003 Management Pack Guide for MOM 2000 SP1 (http://go.microsoft.com/fwlink/?LinkId=47573).