Advisors not working in a high availability setup after a network outage
 Technote (troubleshooting)
 
Problem(Abstract)
On Windows, advisors do not work after a network outage in a high availability setup.
 
Resolving the problem
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.

 
 
Cross Reference information
Segment Product Component Platform Version Edition
Application Servers WebSphere Edge Server Load Balancer Windows 2000 Edge Server 2.0 GA, Edge Server 2.0 NLV, Edge Server 2.0 PTF1
Application Servers Runtimes for Java Technology Java SDK
 
Historical Number
84204
 
 


Document Information


Product categories: Software > Application Servers > Distributed Application & Web Servers > WebSphere Application Server > Edge Component
Operating system(s): Windows
Software version: 5.0
Software edition:
Reference #: 1082862
IBM Group: Software Group
Modified date: Jan 14, 2004