The Microsoft Windows NT 4.0 Resource Kit contains a very powerfulcommand-line utility to test secure channels between Windows NT computersthat are members of a domain, and between domain controllers that aretrusting other domains. Below is a detailed discussion.
Nltest.exe is a very powerful command-line utility that can be used totest trust relationships and the state of domain controller replication ina Windows NT domain. A domain consist of domain controllers in which thereis a single primary domain controller (PDC) and zero or more backup domaincontrollers (BDC).
When the word Trust is used in the context of Windows NT, it describes arelationship between two Windows NT domains. Each domain involved haseither the role of being the trusting domain, or the trusted domain. Forany given trust relationship, there is a single discrete communicationchannel between each domain controller in the trusting domain and a domaincontroller in the trusted domain. For example if Domain "A" trusts Domain"B", then "B" is the trusted domain, and "A" is the trusting domain. In aanother example, suppose Domain "I" trusts Domain "J", and Domain "J"trusts Domain "I". In this example, there are two distinct trustrelationships between the domain controllers. Often, this is called theComplete Trust mode, or a 2-way trust. Yet, for secure channel diagnosis,it is best to think of these as two separate secure channels, between eachdomain controller in the trusting domain and a domain controller in thetrusted domain.
Trust relationships are not transitive. For example, suppose Domain "X"trusts Domain "Y", which in turn trusts Domain "Z". This does NOT implyDomain "X" trusts Domain "Z". The reason for this is that theadministrator in each domain must grant explicit permission on either sideof the trust relationship for it to take place.
Another form of trust relationship is sometimes referred to as an"implicit" trust. In a single domain model, or in an environment wherethere are no "explicit" trust relationships between any two domains, the"implicit" trust relationship is active and functionally needed. Thisimplicit trust exists between all computers running Windows NT that aremembers of a domain and a domain controller in their domain. Explicittrust relationships are established through User Manager For Domains.Implicit trust relationships are established by becoming a member of adomain.
Nltest.exe can be used to test the trust relationship between a computerrunning Windows NT that is a member of a domain and a domain controllerwhere its machine account resides. NLTEST can also verify the trustbetween the BDCs in a domain and their PDC. In domains where an explicittrust has been defined, NLTEST can test the trust relationship between alldomain controllers in the trusting domain and a domain controller in thetrusted domain.
These sessions of communication are called Secure Channels and are used toauthenticate Windows NT machine accounts. They are also used toauthenticate User Accounts when a remote user connects to a networkresource and the user account exists in a trusted Domain. This is calledPass-Through Authentication, and it allows a computer running Windows NTthat has joined a domain to have access to the User Account Database inits domain and in any Trusted Domains.
Nltest.exe can use the Browser Service to enumerate domain controllers.Therefore, if browsing is not working correctly, Nltest.exe may produceinconsistent results. The computer where Nltest.exe is run and thoseproviding the browsing services need to share the same protocols that areused by the domain controllers to carry out their domain activity. Inaddition, the enumeration of the specified computer and domain namesdepend on the status of name-resolution, such as WINS server replication,IPX router configuration, or NetBEUI bridging.
All of these trust relationships, and domain synchronization, can bemonitored, tested, and verified by Nltest.exe.
Sample Output Obtained by Typing "NLTEST.EXE" Without the QuotesC:\NTRESKIT>nltest
Usage: nltest [/OPTIONS]
/SERVER:<ServerName> - Specify <ServerName>
/QUERY - Query <ServerName> netlogon service
/REPL - Force replication on <ServerName> BDC
/SYNC - Force SYNC on <ServerName> BDC
/PDC_REPL - Force UAS change message from <ServerName> PDC
/SC_QUERY:<DomainName> - Query secure channel for <Domain> on <ServerName>
/SC_RESET:<DomainName> - Reset secure channel for <Domain> on <ServerName>
/DCLIST:<DomainName> - Get list of DC's for <DomainName>
/DCNAME:<DomainName> - Get the PDC name for <DomainName>
/DCTRUST:<DomainName> - Get name of DC is used for trust of <DomainName>
/WHOWILL:<Domain>* <User> [<Iteration>] - See if <Domain> will log on <User>
/FINDUSER:<User> - See which trusted <Domain> will log on <User>
/TRANSPORT_NOTIFY - Notify of netlogon of new transport
/RID:<HexRid> - RID to encrypt Password with
/USER:<UserName> - Query User info on <ServerName>
/TIME:<Hex LSL> <Hex MSL> - Convert NT GMT time to ASCII
/LOGON_QUERY - Query number of cumulative logon attempts
/TRUSTED_DOMAINS - Query names of domains trusted by workstation
/BDC_QUERY:<DomainName> - Query replication status of BDCs for <DomainName>
/SIM_SYNC:<DomainName> <MachineName> - Simulate full sync replication
/LIST_DELTAS:<FileName> - display the content of given change log file
/LIST_REDO:<FileName> - display the content of given redo log file
Additional Comments and Descriptions of the Nltest.exe Switches
/SERVER:<ServerName>: Remotes the Nltest.exe command to the specified server. If this switch is not specified, the command is run from the local computer.
/QUERY Queries the local or specified server for a healthy secure channel to a domain controller, and the status of Directory Services replication with the PDC. This is very helpful in determining the general status of the Netlogon service.
/REPL Force partial synchronization of the local or specified BDC.
/SYNC Forces a full, immediate synchronization of the local or specified BDC.
/PDC_REPL The specified PDC forces a change message to all BDCs.
/SC_QUERY:<DomainName> Verifies the secure channel in the specified domain for a local or remote workstation, server, or BDC. This can be run for a PDC if an explicit trust relationship exists between two domains and the trusted domain is specified.
/SC_RESET:<DomainName> Resets the secure channel between the local or remote workstation, server, or BDC. This can be run for a PDC if an explicit trust relationship exists between two domains and the trusted domain is specified.
/DCLIST:<DomainName> Lists all the domain controllers, PDC, and BDCs in a given domain.
/DCNAME:<DomainName> Lists the primary domain controller for a given domain.
/DCTRUST:<DomainName> Queries and tests the secure channel every time the command is executed. Specify the domain for the local or remote workstation, server, or BDC. This can be run for a PDC if an explicit trust relationship exists between two domains and the trusted domain is specified.
/WHOWILL:<Domain><User> Queries the domain and indicates which Domain Controller has the account in their local user account database. This is very useful in determining if a given domain controller contains the user account. If the username specified is that of the currently logged on user, the user's current password is NOT sent to the domain controller. This is helpful in determining if duplicate accounts exist across several domains.
/FINDUSER:<User> Queries explicit trusted domains for the user specified. This is very useful when determining what trusted domain controller or what trusted domain out of several trusted domains will authenticate a user's credentials when a Domain name is not specified in the Server Message Block (SMB) packet. Many down-level clients, such as Windows for Workgroups version 3.1 and the real-mode redirector in Windows 95, do not specify a domain name.
/USER:<UserName> Displays many of the attributes for the specified user account that are maintained in the user account database.
/LOGON_QUERY Specifies the number of attempted logon queries at the console, or over the network.
/TRUSTED_DOMAINS Displays a list of explicit trusted domains.
/BDC_QUERY:<DomainName> List the backup domain controllers in the specified Domain and provides the state of their synchronization.
/LIST_DELTAS:<FileName> List information from the Netlogon.chg file specifying changes to the user account database.
/LIST_REDO:<FileName> List information from the Netlogon.chg file specifying changes to the user account database.
Example Output from Nltest.exe
As an example, suppose the TESTD domain trusts the ESS domain, and acomputer running Windows NT Workstation called TEST3 is a member of theTESTD domain.
NLTEST can be used to show this trust relationship.
C:\>nltest /trusted_domains Trusted domain list: ESS The command completed successfully
To determine the domain controllers in the TESTD domain:
C:\>nltest /dclist:testd List of DCs in Domain testd \\TEST2 (PDC) \\TEST1 The command completed successfully
To determine the domain controllers in the ESS domain:
C:\>nltest /dclist:ess List of DCs in Domain ess \\NET1 (PDC) The command completed successfully
Below are the secure channels between each domain controller in TESTD anda DC in the ESS domain.
C:\>nltest /server:test1 /sc_query:ess Flags: 0 Connection Status = 0 0x0 NERR_Success Trusted DC Name \\NET1 Trusted DC Connection Status Status = 0 0x0 NERR_Success The command completed successfully C:\>nltest /server:test2 /sc_query:ess Flags: 0 Connection Status = 0 0x0 NERR_Success Trusted DC Name \\NET1 Trusted DC Connection Status Status = 0 0x0 NERR_Success The command completed successfully
The workstation that is a member of the TESTD domain has an implicit trustwith a domain controller.
C:\>nltest /server:test3 /sc_query:testd Flags: 0 Connection Status = 0 0x0 NERR_Success Trusted DC Name \\TEST2 Trusted DC Connection Status Status = 0 0x0 NERR_Success The command completed successfully
To determine if a domain controller can authenticate a user account:
C:\>nltest /whowill:ESS bob [20:58:55] Mail message 0 sent successfully (\MAILSLOT\NET\GETDC939) [20:58:55] Response 0: S:\\NET1 D:ESS A:bob (Act found) The command completed successfully C:\>nltest /whowill:testd test [21:26:13] Response 0: S:\\TEST2 D:TESTD A:test (Act found) [21:26:15] Mail message 0 sent successfully (\MAILSLOT\NET\GETDC295) The command completed successfully
NLTEST can be used to find a trusted domain that has a given user account.
C:\>nltest /finduser:sweppler Domain Name: ESS Trusted DC Name \\NET1 The command completed successfully
To verify the status of BDC synchronization:
C:\>nltest /bdc_query:testd Server : \\TEST1 SyncState : IN_SYNC ConnectionState : Status = 0 0x0 NERR_Success The command completed successfully
Nltest.exe can also be used to synchronize the accounts database from acommand line or a batch job.
To run the utility to synchronize the domain from a PDC, type: C:\ nltest /PDC_Repl
To run the utility from a member server, backup domain controller, orWindows NT workstation, type C:\ nltest /Server:<PDCName> /PDC_Repl
where PDCName is the actual name of the PDC, not the name of the domain)
You will see the successful synchronization events in Event Viewer on theprimary domain controller, as well as the backup domain controllers.