When the Microsoft Windows operating system detects a
network outage, by default it clears its Address Resolution Protocol (ARP)
cache, including all static entries. After the network is available, the
ARP cache is repopulated by ARP requests sent on the network.
When Load Balancer or Network Dispatcher is configured with a high
availability setup, both servers, in this setup, takeover primary
operations when a loss of network connectivity affects one or both. When
the ARP request is sent to repopulate the ARP cache, both servers respond,
which causes the ARP cache to mark the entry as not valid. Therefore, the
advisors are not able to create a socket to the backup servers.
Preventing the Windows 2000 operating system from clearing the ARP
cache when there is a loss of connectivity solves this problem. Microsoft
has published an article that explains how to accomplish this task. This
article is on the Microsoft Web site, located in the Microsoft Knowledge
Base, article number 239924 How
to Disable Media Sense for TCP/IP in Windows
Here is a brief summary of the article.
1. Use the Registry editor (regedit or regedit32) to open the registry.
2. View the following key in the registry:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Tcpip\Para
3. Add the following registry value:
Value Name: DisableDHCPMediaSense
Value Type: REG_DWORD
4. After the key is added, edit the value and set it to 1.
5. Restart the machine for the change to take effect.
Note: This affects the ARP cache regardless of what the DHCP
setting is.
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