Settings For Main Office - D-Link DFL-200 - Security Appliance User Manual

Under MPPE encryption 128 bit should be the only checked option.
Leave Use IPSec encryption unchecked
Click Apply
3. Setup policies for the new tunnel, Firewall->Policy:
Click Global policy parameters
Enable Allow all VPN traffic: internal->VPN, VPN->internal and VPN->VPN
Click Apply
4. Click Activate and wait for the firewall to restart.

Settings for Main office

1. Setup interfaces, System->Interfaces:
WAN IP: 194.0.2.20
LAN IP: 192.168.1.1, Subnet mask: 255.255.255.0