Microsoft KB Archive/262143

= INFO: Application Center Cluster Status Heartbeat =

Article ID: 262143

Article Last Modified on 6/4/2003

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APPLIES TO


 * Microsoft Application Center 2000 Standard Edition, when used with:
 * Microsoft Windows 2000 Standard Edition

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This article was previously published under Q262143



SUMMARY
This article describe the cluster heartbeat implemented by Application Center 2000 and how it relates to the &quot;Alive/Dead&quot; and &quot;Online/Offline&quot; status of each cluster member.



MORE INFORMATION
Each member of a given Application Center cluster has an &quot;Alive/Failed&quot; status associated with it. This status is displayed in both the Microsoft Management Console (MMC) and Web-based user interfaces, through one of the member status icons. The cluster controller sends an Internet control message protocol (ICMP) ping to every member at 2-second intervals. Each member has 1 second in which to respond to this ping. If a member doesn't respond to more than two consecutive pings, it is assumed to be &quot;Failed&quot; from a networking perspective. Its status will switch back to &quot;Alive&quot;, if it starts responding again and does so for three consecutive pings. This heartbeat simply verifies that a server can communicate at the Transmission Control Protocol/Internet Protocol (TCP/IP) level.

The &quot;Online/Offline&quot; member status determines if a computer is currently receiving load or not through load balancing. Although the &quot;Alive/Failed&quot; status is determined independently of the &quot;Online/Offline&quot; status, a &quot;Failed&quot; member is usually &quot;Offline&quot; as well. For example, if a member could not be pinged from the cluster controller over any network interface card (NIC), then it is likely not online for network load balancing (NLB) because the load balancer would not be able to contact the computer either.

NOTE: Network Load Balancing also implements its own heartbeat over the &quot;Front End&quot; NICS bound to NLB. This NLB heartbeat is independent of the Application Center cluster heartbeat and is implemented differently. For additional information on the NLB heartbeat, click the article number below to view the article in the Microsoft Knowledge Base:

232711 How Cluster Integrity Is Monitored in WLBS

Applicable Application Center 2000 Event IDs

4023 (Error) - The cluster member failed.

4024 (Informational) - Server is alive.

