Sonicwall Global VPN Client: Sonicwall GVC unable to connect through certain ISPs

In some cases, Sonicwall GVC is unable to connect to select ISPs/Networks, where it is proven working elsewhere (3G Tethering or other ISPs).

Usual troubleshooting and things to look at is if VPN IPSec Passthrough is enabled on the home modem or router.

There is another troubleshooting step that is worth trying, which is to restrict the size of the first ISAKMP packet.


Try reducing the size of the first ISAKMP packet sent by following these steps created using Sonicwall GVC  version (Downgrade if necessary, Download via mysonicwall )

1. Open the SonicWall application

Click -> File -> Properties


-> Enable – “Restrict the size of the first ISAKMP packer sent if this isn’t checked.


  1. Apply the change and close properties.
  2. You will then have to retest your VPN connection.

Known issue for the following ISP:

  1. Foxtel Australia
  2.  —

For upgrade and installation support, please review the Administrator’s Guide for the relevant version of GVC.

Pre-installation recommendations

SONICWALL strongly recommends you follow these steps before installing the Global VPN Client (GVC) 4.9.14 (or higher) client:

  • If you have SONICWALL Global VPN Client version 4.8.6 or earlier installed, you must uninstall that version before installing version 4.9.14. Upgrading to GVC 4.9.14 is supported from version 4.9.0 and higher.
  • SONICWALL encounters run time conflicts when it co-exists with any 3rd party IPsec VPN clients. Uninstall all IPsec VPN clients prior to installing SONICWALL GVC. (Particularly Cisco Legacy VPN Client 5 or Forticlient)
  • For Vista systems, it is required that you update device drivers for each Network Adapter card to the latest available versions. You can check the NIC vendor Web site for these updates.

Sonicwall KB:

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