VPN Clients cannot Ping beyond RRAS Server (DR-Site)

My workaround: manually assign a range of LAN IP in the static route pool.

To create a static IP address pool

1. Open Routing and Remote Access.


2. Right-click the server name for which you want to create a static IP address pool, and then click Properties.


3. On the IP tab, click Static address pool, and then click Add.


4. In Start IP address, type a starting IP address, and then either type an ending IP address for the range in End IP address or type the number of IP addresses in the range in Number of addresses.


5. Click OK, and then repeat steps 3 and 4 for as many ranges as you need to add.

This is a good article on troubleshoot this issue.