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How to configure the loopback adapter on Microsoft Windows 2008.

Technote (troubleshooting)


To use a Microsoft® Windows® 2008 machine as a server that is load balanced by the Edge components Load Balancer for IBM® WebSphere® Application Server using the MAC forwarding method, you must alias the cluster to the loopback adapter.


Aliasing the loopback is different for the Windows 2008 operating system than previous Windows operating systems

Resolving the problem

On Microsoft Windows, you must first install the loopback adapter as it is not installed by default. Instructions for installing the loopback can be found in the Load Balancer Administrator's Guide and has not changed for Windows 2008.

To configure the loopback with the cluster IP, complete the following steps to alias an IPv6 address.

  1. Issue the ipconfig /all command on the command line to determine the interface name of the loopback adapter. Locate the loopback adapter information in the results. For example:
    Ethernet adapter Local Area Connection 2:
    Description ...Microsoft Loopback Adapter

    In the previous example, the interface name is "Local Area Connection 2."
  2. Alias the cluster IP to the loopback using the following netsh command :
    netsh interface ipv4 add address "Local Area Connection 2" cluster_ip_address subnet_mask
  3. Enable forwarding for all of the interfaces on the machine. For example:
    netsh interface ipv4
    set interface "Local Area Connection" forwarding=enabled
    set interface "Local Area Connection 2" forwarding=enabled
    After each command, you should receive an "OK" message.

The Next Generation TCP/IP stack in Windows Vista and Windows Server 2008 supports strong host sends and receives for both IPv4 and IPv6 by default. Hence weak send and receive should be enabled explicitly using following steps: ("loopback" and "interface" names in below commands are imaginary and should be replaced either by correct name or index number on your system.)
  • netsh interface ipv4/ipv6 set interface "loopback" weakhostreceive=enabled
  • netsh interface ipv4/ipv6 set interface "loopback" weakhostsend=enabled
  • netsh interface ipv4 set interface "interface" weakhostreceive=enabled

Document information

More support for: WebSphere Application Server
Edge Component

Software version: 7.0, 8.0, 8.5, 8.5.5

Operating system(s): Windows

Software edition: Edition Independent

Reference #: 1304795

Modified date: 10 November 2010