Microsoft KB Archive/233279

= How WLBS Handles the Dedicated IP Address =

Article ID: 233279

Article Last Modified on 2/27/2007

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APPLIES TO


 * Microsoft Windows 2000 Advanced Server
 * Microsoft Windows NT Server 4.0 Enterprise Edition
 * Microsoft Windows NT Load Balancing Service

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This article was previously published under Q233279





SUMMARY
The dedicated Internet Protocol (IP) address you configure during Windows NT Load Balancing Service (WLBS) or Windows 2000 Network Load Balancing (NLB) Setup is the local host's unique IP address used for dedicated traffic to the host or network traffic not associated with the cluster. The WLBS or NLB driver passes all packets addressed to the dedicated IP to the TCP/IP stack.



MORE INFORMATION
There are two types of dedicated traffic:
 * Intracluster (among cluster hosts)
 * Intercluster (between individual cluster hosts and external clients or servers)

Because individual servers can be tested through their dedicated address, you can use the dedicated IP address to diagnose bad content. You can also use Telnet to access a specific host within the cluster.

WLBS and NLB use the dedicated IP address when you use a single network adapter to handle both cluster network traffic and dedicated traffic. In this case, the cluster's IP address and the dedicated IP address are bound to the same network adapter. WLBS and NLB ensure that all traffic to the dedicated IP address is not affected (even when the WLBS or NLB host is not part of a cluster because of problems).

NetBT (NetBIOS over TCP/IP) binds only to the first IP address on a network adapter. When you use a single network adapter, the first IP address is either the cluster IP address or the dedicated IP address. If an IP address is not the first one listed, it does not communicate using NetBT.

An additional network adapter is recommended for separating cluster and dedicated traffic on each host. If you use separate network adapters to handle cluster network traffic and dedicated traffic, only the cluster's network adapter is bound to the WLBS or NLB driver. Network traffic to the dedicated IP address is not associated with the WLBS or NLB driver.

