Using VPN to get license from License Server

Technical Note 88251






4/20/2023 5:45 PM


There is no license fetched over the VPN connection.

Applies to

This Technical Note applies to IAR System products that uses License Management System version 2 (LMS2). Most of the products were updated to LMS2 during 2012-2013.


  • IAR does not support the VPN connection itself, that is, when it comes to problems using/setting up VPN involve the IT Department and/or the VPN provider.
  • Present versions will accept VPN connections.
  • Please note that fetching a licenses over VPN must comply to the terms in the Software License Agreement for IAR Embedded Workbench.
  • Older versions of IAR products (using License Management System version 1) will NOT accept to fetch a license using VPN connections.

Possible actions

Having all the above said, these are some generic suggestions on troubleshooting VPN that we have obtained from various customer IT departments:

  • Check that the port UDP 5093 is open all the way from the Client Computer through VPN, firewall(s), router(s) etc. to the License Server Computer.
  • Follow the Recommendations for Successful Communication from THALES  (MTU size 1474).
  • Ask the VPN expert at the IT department to examine size of the VPN packets - IAR Systems has seen cases where the VPN packet, that reaches the Client Computer is truncated, and thus the license isn't valid.
    • The VPN expert can try to reduce the MTU size on the license server computer only (to make it send smaller packets).
    • An MTU size of 1359 (on the server computer) made one VPN connection work.
    • The VPN expert can try to make an VPN-rule to "enable fragmented packages"...
    • ...and also make a Firewall-rule to "enable fragmented packages".
  • Regarding MTU sizes, a suggested test procedure we received is the following. Note that this information is provided "as is" - we cannot provide any support on the procedure below.
    ping <server ip address> -f -l 1244​
    • The ping command above is a test to determine highest MTU Setting
      from the client to server before packet fragmentation occurs.

      If ping result responds normally increase MTU value above.

      If ping result fails with "Packet needs to be fragmented but DF Set" decrease the MTU value above.
  • If the VPN connection can't be established - Then you may consider the use of a commuting license. See chapter Checking out a product for commuter authorization in:
    <installation directory>\common\doc\EW_LicensingGuide_LMS2.ENU.pdf​

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