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Disable NetBIOS with care

Many admins want to disable NetBios over TCP/IP for security and other reasons. But you will face a new set of concerns where Exchange 2000 and 2003 are in use.

NetBIOS name resolution translates IP addresses of computers on your local-area network into NetBIOS names, which are the machine names used by Microsoft Networking and Windows File and Printer Sharing.

Many administrators are growing keen on disabling NetBIOS over TCP/IP for a number of reasons. Security, network overhead and doing away with the legacy requirements of NetBIOS in the first place are three big ones.

Unfortunately, disabling NetBIOS traffic in environments where Exchange 2000 or 2003 Server are in use can cause Exchange's functionality to degrade if DNS and WINS are not being used for name resolution.

The most significant breaks in functionality will come from clustered systems, but other common functions -- EXMERGE, changing passwords for a mailbox through Outlook Web Access, Outlook clients earlier than Outlook 2003 that use Exchange, the Exchange System Manager -- may also break. Also, not using NetBIOS can cause name collision problems in a heterogeneous network unless each computer in the network can access FQDN information from the DNS server (or, if the computer is running Exchange 5.5 or NT 4.0, it needs to access a WINS server).

NetBIOS may be something that can be done away with in a wholly homogenous domain environment. This means using the most recent versions of Exchange, Windows Server and Outlook across the board. (Exchange 5.5, for instance, will not work without NetBIOS or WINS.) But this is still not a guarantee: the burden of regression-testing programs to work without NetBIOS is going to fall on the administrator who decides to do without it.

Microsoft has pointed out that future versions of Exchange and other Windows server technologies should work correctly without NetBIOS, but the best way to be sure is to do controlled testing in a standalone domain.


Serdar Yegulalp is the editor of the Windows 2000 Power Users Newsletter.


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