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Configure a Multi-Forest Deployment

Published: August 15, 2012

Updated: August 15, 2012

Applies To: Windows Server 2012, Windows Server 2012 R2



This topic describes how to configure a Remote Access multi-forest deployment in several possible scenarios. All of the scenarios assume that DirectAccess is currently deployed on a single forest called Forest1, and that you are configuring DirectAccess to work with a new forest called Forest2.

In this scenario, DirectAccess is already deployed on Forest1, and is configured to allow clients from Forest1 to access the corporate network. By default, clients connected via DirectAccess can access only resources in Forest1 and cannot access any servers in Forest2.

  1. If the DNS suffix of Forest2 is not part of the DNS suffix of Forest1, add NRPT rules with the suffixes of the domains in Forest2, and optionally, add the suffixes of the domains in Forest2 to the DNS suffix search list. See Add NRPT rules and DNS suffixes.

  2. Add the relevant internal IPv6 prefixes in Forest2 if IPv6 is deployed on the internal network. See Add internal IPv6 prefix.

In this scenario, you configure the Remote Access deployment to allow clients from Forest2 to access the corporate network. It is assumed that you have created the required security groups for client computers in Forest2. For information about the required security groups, see Plan client security groups.

  1. Add the security group of the clients from Forest2. See Add client security groups.

  2. If the DNS suffix of Forest2 is not part of the DNS suffix of Forest1, add NRPT rules with the suffixes of the clients’ domain in Forest2 to enable access to the domain controllers for authentication, and optionally, add the suffixes of the domains in Forest2 to the DNS suffix search list. See Add NRPT rules and DNS suffixes.

  3. Add the internal IPv6 prefixes in Forest2 to enable DirectAccess to create the IPsec tunnel to the domain controllers for authentication. See Add internal IPv6 prefix.

  4. Refresh the management servers list. See Refresh the management servers list.

In this scenario, DirectAccess is deployed in a multisite configuration on Forest1, and you want to add a Remote Access server, named DA2, from Forest2 as an entry point to the existing DirectAccess multisite deployment.

  1. Make sure that the Remote Access administrator has sufficient permissions to write GPOs on the domain of DA2, and that the Remote Access administrator is a local administrator on DA2.

  2. Add DA2 as an entry point. See 3.7. Add entry points to the multisite deployment.

  3. Add NRPT rules with the suffixes of the domains in Forest2 to enable access to the domain controllers for authentication, and optionally, add the suffixes of the domains in Forest2 to the DNS suffix search list. See Add NRPT rules and DNS suffixes.

  4. Add the relevant internal IPv6 prefixes in Forest2, if required, to enable Remote Access to establish the IPsec tunnel to the corporate resources and to make sure that NCSI probes work correctly. See Add internal IPv6 prefix.

  5. Refresh the management servers list. See Refresh the management servers list.

Note the following terms when configuring OTP in a multi-forest deployment:

  • Root CA—The forest(s) main PKI tree CA.

  • Enterprise CA—All other CAs.

  • Resource Forest—The forest that contains the Root CA, and is considered to be the ‘Managing forest\domain’.

  • Account Forest—All other forests in the topology.

The PowerShell script, PKISync.ps1, is required for this procedure. See AD CS: PKISync.ps1 Script for Cross-forest Certificate Enrollment.

noteNote
This topic includes sample Windows PowerShell cmdlets that you can use to automate some of the procedures described. For more information, see Using Cmdlets.

  1. Enable LDAP referral support on all of the enterprise CAs in all of the forests by running the following command from an elevated command prompt:

    certutil -setreg Policy\EditFlags +EDITF_ENABLELDAPREFERRALS
    
  2. Add all enterprise CA computer accounts to the Active Directory Cert Publishers security groups in each of the account forests.

  3. Restart all of the certsvc services on all of the CA computers in all of the forests by running the following command from an elevated command prompt:

    net stop certsvc && net start certsvc
    
  4. Extract the root CA certificate by running the following command from an elevated command prompt:

    certutil -config <Computer-Name>\<Root-CA-Name> -ca.cert <root-ca-cert-filename.cer>
    

    (If you run the command on the root CA you can omit the connection information, -config <Computer-Name>\<Root-CA-Name>)

    1. Import the Root CA certificate from the previous step on the Account Forest CA by running the following command from an elevated command prompt:

      certutil -dspublish -f <root-ca-cert-filename.cer> RootCA
      
    2. Grant Resource Forest certificate templates Read/Write permissions to the <Account Forest>\<Administrator account>.

    3. Extract all resource forest enterprise CA certificates by running the following command from an elevated command prompt:

      certutil -config <Computer-Name>\<Enterprise-CA-Name> -ca.cert <enterprise-ca-cert-filename.cer>
      

      (If you run the command on the root CA you can omit the connection information, -config <Computer-Name>\<Root-CA-Name>)

    4. Import the Enterprise CA certificates from the previous step on the Account Forest CA by running the following commands from an elevated command prompt:

      certutil -dspublish -f <enterprise-ca-cert-filename.cer> NTAuthCA
      certutil -dspublish -f <enterprise-ca-cert-filename.cer> SubCA
      
    5. Remove account forest OTP certificate templates from the list of issued Certificate Templates.

  1. Delete OTP certificate templates from the Account Forest; that is, Forest2.

  2. Copy certificate templates and Oid objects from the Resource Forest to each of the Account Forests using the following PowerShell commands:

    .\PKISync.ps1 -sourceforest <resource forest DNS> -targetforest <account forest DNS> -type Template -cn <DA OTP registration authority template common name>.
    .\PKISync.ps1 -sourceforest <resource forest DNS> -targetforest <account forest DNS> -type Template -cn <Secure DA OTP logon certificate template common name>.
    .\PKISync.ps1 -sourceforest <resource forest DNS> -targetforest <account forest DNS> -type Oid –f
    

  • Issue the newly imported certificate templates on all Account Forests CAs.

  1. Extract all Enterprise CA certificates from the Account Forests by running the following commands from an elevated command prompt:

    certutil -config <Computer-Name>\<Enterprise-CA-Name> -ca.cert <enterprise-ca-cert-filename.cer>
    
  2. Synchronize CAs across forests from the Account Forests to the Resource Forest using the following PowerShell command:

    .\PKISync.ps1 -sourceforest <account forest DNS> -targetforest <resource forest DNS> -type CA -cn <enterprise CA sanitized name> –f
    
  3. Synchronize CAs across forests from the Resource Forest to the Account Forests using the following PowerShell command:

    .\PKISync.ps1 -sourceforest <resource forest DNS> -targetforest <account forest DNS> -type CA -cn <enterprise CA sanitized name> –f
    

The following sections contain the configuration procedures for the above scenario deployments. After completing a procedure, return to the scenario to continue.

Clients that connect via DirectAccess to the corporate network use the Name Resolution Policy Table (NRPT) to determine which DNS server should be used to resolve the address of different resources. This allows the client to resolve corporate resource addresses and helps the client maintain a proper inside-corporate/outside-corporate classification, which is required to keep DirectAccess working. The DirectAccess configuration tools automatically detect the root DNS suffix of Forest1 and add it to the NRPT table. However, the FQDN suffixes of Forest2 are not added automatically to the NRPT table, and the Remote Access administrator must add them manually.

The DNS suffix search list allows the clients to use short label names instead of FQDNs. The Remote Access configuration tools automatically add all the domains in Forest1 to the DNS suffix search list. If you want to enable clients to use short label names for resources in Forest2, you need to add them manually.

  1. In the middle pane of the Remote Access Management console, in the Step 3 Infrastructure Servers area, click Edit.

  2. On the Network Location Server page, click Next.

  3. On the DNS page, in the table, enter any additional name suffixes that are part of the corporate network in Forest 2. In DNS Server Address, enter the DNS server address manually, or by clicking Detect. If you don’t enter the address, the new entries are applied as NRPT exemptions. Then click Next.

  4. Optional: On the DNS Suffix Search List page, add any DNS suffixes by entering the suffix in the New Suffix box, and then clicking Add. Then click Next.

  5. On the Management page, click Finish.

  6. In middle pane of the Remote Access Management console, click Finish.

  7. On the Remote Access Review dialog box, click Apply.

  8. On the Applying Remote Access Setup Wizard Settings dialog box, click Close.

noteNote
Adding an internal IPv6 prefix is relevant only when IPv6 is deployed on the internal network.

Remote Access manages a list of IPv6 prefixes for corporate resources. Only resources with these IPv6 prefixes may be accessed by clients that are connected via DirectAccess. Because the Remote Access Management console and Windows PowerShell commands automatically add the IPv6 prefixes of Forest1, and might not add the prefixes of other forests, you must add any missing prefixes of Forest2 manually.

  1. In the middle pane of the Remote Access Management console, in the Step 2 Remote Access Server area, click Edit.

  2. In the Remote Access Server Setup wizard, click Prefix Configuration.

  3. On the Prefix Configuration page, in Internal network IPv6 prefixes, add any additional IPv6 prefixes separated by semicolons, for example, 2001:db8:1::/64;2001:db8:2::/64. Then click Next.

  4. On the Authentication page, click Finish.

  5. In middle pane of the Remote Access Management console, click Finish.

  6. On the Remote Access Review dialog box, click Apply.

  7. On the Applying Remote Access Setup Wizard Settings dialog box, click Close.

To enable Windows 8 client computers from Forest2 to access resources through DirectAccess, you must add the security group from Forest2 to the Remote Access deployment.

  1. In the middle pane of the Remote Access Management console, in the Step 1 Remote Clients area, click Edit.

  2. In the DirectAccess Client Setup wizard, click Select Groups, and then on the Select Groups page, click Add.

  3. On the Select Groups dialog box, select the security groups containing DirectAccess client computers. Then click Next.

  4. On the Network Connectivity Assistant page, click Finish.

  5. In middle pane of the Remote Access Management console, click Finish.

  6. On the Remote Access Review dialog box, click Apply.

  7. On the Applying Remote Access Setup Wizard Settings dialog box, click Close.

To enable Windows 7 client computers from Forest2 to access resources through DirectAccess when multisite is enabled, you must add the security group from Forest2 to the Remote Access deployment for each entry point. For information about adding Windows 7 security groups, see the description of the Client Support page in 3.6. Enable the multisite deployment.

Remote Access automatically discovers the infrastructure servers in all the forests that contain DirectAccess configuration GPOs. If DirectAccess was deployed on a server from Forest1, the server GPO will be written to its domain in Forest1. If you enabled access to DirectAccess for clients from Forest2, the client GPO will be written to a domain in Forest2.

The automatic discovery process of infrastructure servers is required to allow access through DirectAccess to the domain controllers and System Center Configuration Manager. You must manually start the discovery process.

  1. In the Remote Access Management console, click Configuration, and then in the Tasks pane, click Refresh Management Servers.

  2. On the Refreshing Management Servers dialog box, click Close.

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