In larger Microsoft Exchange Server 2003 organizations and larger Microsoft Exchange 2000 Server organizations, some operations do not work correctly if NetBIOS name resolution is not working on the network.
Exchange 2003 and Exchange 2000 still have several NetBIOS dependencies. You may have to use NetBIOS name resolution across different subnets for the successful operation of all Exchange components, depending on the network topology.
Microsoft recommends that Exchange organizations use Windows Internet Name Service (WINS) and DNS for name resolution. Installations of Exchange 2003 and Exchange 2000 in large and subnetted organizations without WINS have not been fully tested. In large organizations, NetBIOS name resolution through broadcasts may not function correctly. Some Exchange functionality may also be affected.
The following Exchange functionality still depends on WINS name resolution:
- The Exchange Server 2003 Setup program and the Exchange 2000 Server Setup program, especially on clustered servers.
- Exchange Mailbox Merge Wizard (ExMerge) on an Exchange 2003 computer and on an Exchange 2000 computer.
- Changing a password for an Exchange 2003 mailbox or an Exchange 2000 mailbox through Microsoft Outlook Web Access (OWA).
- Exchange System Manager on an Exchange 2003 computer and on an Exchange 2000 computer.
Note Additionally, Microsoft Outlook clients that are earlier than Microsoft Office Outlook 2003 also require NetBIOS name resolution.
The following list summarizes the recommendations for placement of Active Directory domain controllers and global catalog servers to support your Exchange organization:
Exchange 2003 uses Windows name resolution APIs to look up "short names," also known as NetBIOS names. Therefore, the server expects to resolve short names during operation, the ESM client expects to resolve short names when contacting servers, and Outlook clients that are earlier than Outlook 2003 expect to resolve the short name of a server. Unless all clients and servers are on the same subnet, the easiest way for short name resolution to work is to set up a WINS server.
- Make sure that DNS is correctly configured at the hub site and on all branches.
- Make sure that name resolution and DNS functionality are both operating correctly.
- Make sure that the infrastructure master role is not on a global catalog server.
- In branch offices that service more than 10 users, one global catalog server must be installed in each location that contains Exchange servers, and Microsoft recommends that you deploy two global catalog servers for redundancy. If a physical site does not have two global catalog servers, you can configure existing domain controllers as global catalog servers.
Server clustering in Microsoft Windows Server 2003, Microsoft Windows 2000 Server, and Microsoft Windows NT Server 4.0 requires NetBIOS, but server clustering does not necessarily require WINS for name resolution. If you use a DNS server that supports the dynamic update protocol for virtual servers, server clusters register "A" resource records in DNS. Then clients can query DNS to resolve the virtual server's IP address. However, you cannot keep server clusters from creating NetBIOS over TCP/IP objects for the virtual servers.
Name collisions cannot occur when you use WINS. In a WINS environment, only one computer can be named SERVERA. In DNS, multiple computers can be named SERVERA. For example, one computer may be named SERVERA.EUROPE.DOMAIN.COM and another computer may be named SERVERA.AMERICA.DOMAIN.COM. If a user who is located in the AMERICA domain types \\SERVERA, they connect to SERVERA in the AMERICA domain. If a user who is located in the AMERICA domain wants to connect to SERVERA in the EUROPE domain, that user must specify the fully qualified domain name (FQDN) SERVERA.EUROPE.DOMAIN.COM. Some programs may only permit entries with a maximum of 15 characters for NetBIOS names. These programs may still work if a mechanism exists to avoid duplicate host names and if the DNS suffix list of domains is provided to all clients.
Although Windows Server 2003 and Exchange Server 2003 use FQDNs and DNS for name resolution, Windows NT 4.0 and Microsoft Exchange Server 5.5 use NetBIOS and WINS for host name resolution. If the computer does not have a LMHOSTS file, there must be a WINS server available for the Exchange 5.5 computer to communicate with the Exchange 2003 computer.
Many programs may work with NetBIOS disabled but do not support this type of configuration. For example, Exchange 2003 and Exchange 2000 were not tested without NetBIOS, but they may work without NetBIOS in a flat domain environment.
By default, in Windows Server 2003 the Messenger service and the Alerter service are disabled. For network messages to be transmitted in Windows Server 2003, you must enable and start these services, and the recipient account registration must exist in WINS.
For more information about WINS, visit the following Microsoft Web site: