For a DirectAccess deployment, the Network Location Server (NLS) is an infrastructure component that allows DirectAccess clients to determine if they are inside or outside of the corporate network. If the DirectAccess client can successfully connect to the NLS, it is on the internal network and DirectAccess is not used. If the NLS cannot be contacted, the client is outside of the network and will attempt to establish remote corporate network connectivity using DirectAccess.
It is recommended that the NLS be made highly available by deploying at least two servers in a load balanced configuration to avoid potential service disruptions for DirectAccess clients inside the corporate network. While this approach is sufficient for networks that are contained in a single physical location, it does present some challenges for large organizations with internal networks that span multiple physical locations.
For DirectAccess, only a single NLS URL can be configured per DirectAccess deployment, as shown here.
If a WAN outage occurs on an internal network that spans multiple physical locations, internal DirectAccess clients in locations other than where the NLS resides will mistakenly believe they are outside of the corporate network. This can lead to degraded performance and potential loss of connectivity. NLS reliability can still be improved when the internal network spans multiple physical locations by deploying NLS at each physical location and configuring clients to use a local NLS. This will keep traffic off of the WAN and prevent service disruptions in the event of a WAN outage.
There are several strategies that can be used to configure internal DirectAccess clients to use a local NLS, including DNS round robin, a network load balancer, or Active Directory Group Policy. Using DNS or a load balancer requires only a single NLS URL. Using Active Directory Group Policy requires a unique NLS URL per physical location.
The simplest way to enable DirectAccess clients to use a local NLS is to use DNS round robin and take advantage of subnet prioritization. To do this, create an “A” resource record in DNS that resolves to the IPv4 address for each NLS. On the DNS server, open the DNS Manager, right-click the DNS server and choose Properties. Click the Advanced tab and select the options to Enable round robin and Enable netmask ordering.
This will ensure that name resolution requests for the NLS FQDN will be returned with the nearest NLS. More information about DNS netmask ordering can be found here.
A Global Server Load Balancing (GSLB) solution can also be employed to route requests to a local NLS. Examples include F5 Global Traffic Manager (GTM) and Kemp Technologies LoadMaster GEO. Prescriptive guidance for configuring the Kemp LoadMaster for this scenario can be found here.
This method involves creating unique NLS URLs per site and overriding the default DirectAccess client configuration using Active Directory Group Policy. Separate Group Policy Objects (GPOs) are created and linked to Active Directory Sites to assign a local NLS to internal DirectAccess clients. To accomplish this, create a new GPO for each location where NLS will reside. Edit the GPO and navigate to Computer Configuration/Policies/Administrative Templates/Network/Network Connectivity Status Indicator. Double-click Specify domain location determination URL, choose Enabled, and then enter the URL that corresponds to the NLS for that location.
In the Remote Access Management Console, edit the Infrastructure Server Setup (Step 3) and add the FQDN for each NLS. Do not specify a DNS server. This effectively creates a Name Resolution Policy Table (NRPT) exemption so the NLS cannot be reached when the DirectAccess client is connected remotely.
In the Group Policy Management Console right-click on Sites and choose Show Sites.
Select each Active Directory site where NLS will reside.
Link the GPOs for each NLS to the corresponding site, then right-click the linked GPO and choose Enforced.
Note: Do not install the NLS on a domain controller! By design, the NLS is not reachable remotely by DirectAccess clients. This can lead to potential authentication issues and may prevent DirectAccess clients from connecting successfully.
To confirm that a client computer has been configured to use a local NLS, verify the currently associated Active Directory site by issuing the following command on the DirectAccess client computer:
Next, confirm the setting of the NLS by issuing the following command:
As a reference, here are examples from two DirectAccess clients in two different internal physical locations:
The limitation of a single Network Location Server (NLS) URL for a DirectAccess deployment presents some challenges for DirectAccess architects seeking to eliminate single points of failure in their design. Using the techniques described in this article, administrators can ensure that DirectAccess clients will always connect to a local NLS, eliminating potential failure points and improving the overall reliability of the solution.