Using a hardware router prevents synchronization when the mobile device is cradled.
Cause: If the server is configured with a single network card and a hardware firewall, routers that have built-in IP spoofing protection do not allow internal client computers to connect to the external domain.
Solution: Consult with your hardware provider for updated firmware for your specific device. As an alternative, you can add a DNS zone to bypass IP spoofing by some hardware routers.
To add a DNS zone
Click Start, click Run, and then type dnsmgmt.msc. The DNS Management Console appears.
Double-click your server name in the console tree.
In the details pane, right-click Forward Lookup Zone, and then click New Zone. The New Zone Wizard appears. Click Next.
On the Zone Type page, select Primary Zone, clear the Store the zone in Active Directory (available only if DNS Server is a domain controller) check box, and then click Next.
On the Zone Name page, in the Zone Name box, type the fully qualified domain name of your external domain (for example, www.externaldomainname.com), and then click Next.
On the Zone Files page, click Next.
On the Dynamic Update page, select Do not allow dynamic updates, and then click Next.
Click Finish to close the New Zone Wizard.
Right-click the new zone in the DNS Management Console details pane, and then click New Host (A). The New Host dialog box appears.
Leave the Name field empty. In the IP address box, type the Server Local Area IP address, and then click Add Host.
Click OK, and then click Done to close the New Host dialog box.