By default, the DirectAccess Setup Wizard creates Group Policy objects for DirectAccess clients and servers for settings that allow the following behaviors:
These default settings allow Teredo-based DirectAccess clients to perform Teredo discovery of intranet resources. However, these settings also allow the following:
To prevent these possible security issues, you can modify the default configuration for the following:
With these modifications:
Although these modifications address the security issues of the default configuration, Teredo discovery messages can no longer pass through the DirectAccess server and DirectAccess clients cannot use Teredo as a connectivity method. Therefore, if you make these changes, you must also do the following:
Without Teredo connectivity, DirectAccess clients that are located behind network address translators (NATs) will use Internet Protocol over Secure Hypertext Transfer Protocol (IP-HTTPS) for IPv6 connectivity to the DirectAccess server. However, IP-HTTPS-based connections have lower performance and higher encryption and protocol overhead than Teredo-based connections.
As described in above, the default settings created by the DirectAccess Setup Wizard allow the following:
To complete the following procedure , you must be a member of the Domain Administrators group, or otherwise be delegated permissions to modify Group Policy settings. Review details about using the appropriate accounts and group memberships at Active Directory Default Groups (http://go.microsoft.com/fwlink/?LinkId=83477).
WARNING: The following custom settings must be applied each time you run the DirectAccess wizard. This applies to both the Windows DirectAccess Wizard and the UAG DirectAccess Wizard. If you make policy changes using the DirectAccess Wizard and deploy the new policies to the DirectAccess server(s) and clients, you must perform the following procedure after making the policy changes. If you do not perform the following procedure each time after making a policy change through the Windows or UAG DirectAccess wizard, your settings will be overwritten and IPv6 ICMP traffic will again be allowed to travel in the clear and outside of an IPsec tunnel mode tunnel.
To confine ICMPv6 traffic to the intranet
On a domain controller, start a command prompt as an administrator.
From the Command Prompt window, run the netsh –c advfirewall command.
From the netsh advfirewall prompt, run the following commands:
set store gpo=" DomainName \DirectAccess Policy-{3491980e-ef3c-4ed3-b176-a4420a810f12}"
consec show rule name=”DirectAccess Policy-ClientToDnsDc”
consec show rule name=”DirectAccess Policy-ClientToCorp”
From the display of the last two commands, copy or write down the IPv6 addresses for the RemoteTunnelEndpoint.
set global ipsec defaultexemptions neighbordiscovery,dhcp
consec add rule name=”Exempt ICMPv6 to Tunnel endpoint” profile=private,public action=noauthentication mode=tunnel endpoint1=any endpoint2= IPv6AddressesOfTheRemoteTunnelEndpoints protocol=icmpv6
set store gpo=" DomainName \DirectAccess Policy-{ab991ef0-6fa9-4bd9-bc42-3c397e8ad300}"
consec add rule name=”Exempt ICMPv6 from Tunnel endpoint” profile=private,public action=noauthentication mode=tunnel endpoint1= IPv6AddressesOfTheRemoteTunnelEndpoints endpoint2=any protocol=icmpv6
Click Start, type gpmc.msc, and then press ENTER.
In the console tree, open Forest/Domains/YourDomain, right-click the DirectAccess Policy-{3491980e-ef3c-4ed3-b176-a4420a810f12} GPO, and then click Edit.
In the console tree of the Group Policy Management Editor, open Computer Configuration/Policies/Windows Settings/Security Settings/Windows Firewall with Advanced Security.
Right-click Windows Firewall with Advanced Security, and then click Properties.
Click the IPsec Settings tab. In IPsec exemptions, in Exempt ICMP from IPsec, click No, and then click OK.
Close the Group Policy Management Editor.
In the console tree of the Group Policy Management console, open Forest/Domains/YourDomain, right-click the DirectAccess Policy-{ab991ef0-6fa9-4bd9-bc42-3c397e8ad300} GPO, and then click Edit.