Domain controllers with the highest priority are contacted first. When domain controllers have the same priority, the domain controllers with the highest weight are most likely to be contacted.

When you use the Registry Editor, on a domain controller, to set the priority and weight, Net Logon records these values in the LDAP SRV records that it writes.

NOTE: If you set priority and/or weight, you can view these values in the %SystemRoot%\System32\Config\netlogon.dns file.

To set priority and/or weight of a domain controller, use the Registry Editor to navigate to:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Netlogon\Parameters.

The priority is recorded in the LdapSrvPriority Value Name, a REG_DWORD data type. The highest priority is the lowest number, 0x0, which is the default data value. The permitted range is 0x0 - 0xFFFF. Lower priority domain controllers will only be contacted when the higher priority domain controllers are NOT available.

The weight is recorded in the LdapSrvWeight Value Name, a REG_DWORD data type. When domain controllers have the same priority (LdapSrvPriority), domain controllers with a numerically higher weight are favored, using the following formula:

Probability of Contact = LdapSrvWeight / SUM of all LdapSrvWeight for DCs with the same LdapSrvPriority

Example: If three domain controllers have the highest priority (LdapSrvPriority = 0x0), the probability of contact is:

<b>Server Weight Probability</b>
 A        3    1/2 (3/6)
 B        2    1/3 (2/6)
 C        1    1/6 (1/6)
NOTE: If all the domain controllers of a given priority have the same weight, the data value of LdapSrvWeight is 0x0, by convention.