Communication issue between Service Desk Primary and Secondary Servers caused by MS Patch and Hosts file config.

Document ID : KB000019028
Last Modified Date : 14/02/2018
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Description:

When using Service Desk in a primary/secondary environment, there may be problems encountered in communication between the two servers when running Windows 2008 R2 and using a hosts file.

The concern manifests with the presence of a hosts file on the primary server (located in C:\WINDOWS\system32\drivers\etc) and application of MS patch "MS12-032: Vulnerability in TCP/IP could allow elevation of privilege" (KB 2688338). If the given MS patch is in place, certain hosts file configurations which contain a reference to the loopback address "127.0.0.1" will cause a disruption in Primary/Secondary server communications:

Example of such a hosts file ("server1" is the name of the primary server):

100.100.100.100 server1
127.0.0.1 server1
200.200.200.200 domain.com

Solution:

The observation is that before application of patch KB 2688338, the hosts file will be read from top to bottom, but with the patch in place, the hosts file will be read from bottom to top, causing access to "server1" to be attempted via the loopback address, causing the disruption in communication between certain devices, such as the primary and secondary server.

The suggestion is to either change the order of the entries in the hosts file, or remove the reference to the loopback address, with verification of system and site requirements.