Knowledgebase: VPN and Remote Access
My LAN-to-LAN VPN connects, but no data seems to be going through it
Posted by Gabriel Yu on 02 April 2008 03:29 AM
Check whether both locations are using the same IP Addresses range (e.g. the default 192.168.1.x range).  If so, when the router receives a packet for say 192.168.1.12 it can't know if it should send it to the local 192.168.1.12, or should send it through the VPN tunnel to a remote machine with address 192.168.1.12. 

This is easily solved by:

  • Change the IP Address range at one location to 192.168.2.x.
    1. From the DrayTek's Main Menu, select "LAN TCP/IP and DHCP Setup".
    2. On the left-hand side under the "LAN IP Network Configuration" heading, change the "For NAT Usage" "1st IP Address" to 192.168.2.1.
    3. On the right-hand side under "DHCP Server Configuration" heading, change "Start IP Address" to 192.168.2.20 and "Gateway IP Address" to the new "1st IP Address" value.
    4. From the DrayTek's Main Menu, select "VPN and Remote Access Setup" then "PPP General Setup".
    5. On the right-hand side under the heading "IP Address Assignment for Dial-In Users", change "Start IP Address" to 192.168.2.200.
  • Change the VPN profile at the other end to match this.
    1. From the DrayTek's Main Menu, select "VPN and Remote Access Setup" then "LAN-to-LAN Profile Setup" and the Index number for this VPN profile.
    2. Under "4. TCP/IP Network Settings", change the "Remote Network IP" field to 192.168.2.1.
Note that ALL the LANs which you want to connect will need to have different IP Address ranges.  The instructions above use 192.168.2.x, but you can choose any value from 1 to 254 for the third number. 

Note that this does not apply to Remote User (Teleworker) Profiles, because the teleworkers VPN connection is automatically allocated a temporary local IP address (set at steps 4 and 5 above).
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