Firmware for GSC3510/GSC3505 released as official



Dear Grandstream Customers,

Firmware for GSC3510/GSC3505 is now released as official. Here is the link to the release notes:

The firmware and release notes can be downloaded from:

Please contact us should you have any issues. Thank you for your support for Grandstream products.

Technical Support
Grandstream Networks, Inc.



Hello! I currently have a client with an environment of 40+ GSC3510’s distributed to multiple physical locations that have all begun experiencing this specific issue of “502, Bad Gateway, Unregistered” to their remote VoIP Server, configured in STUN Mode. Once encountered I began reviewing the forums at length and can provide the following information from an aggregation of two forum posts and this firmware’s beta release post:

  • History: Issue began occurring somewhere between firmware and As that the current firmware version is and the last two downloads available are and for “previous firmwares”, this limits the ability to revert to previous functioning firmware.

  • Solution 1: During this firmware timeframe, the default TLS version changes from 1.0 to 1.1. A user proposed that this resolved the issue for them - myself and another forum member tested and were not able to replicate.

  • Solution 2: Another solution proposed was to change the provisioning link to use static IP address which resolved the issue for them - I tested and was not able to replicate.

  • Solution 3 (Current Fix): Not a confirmed solution, but a question from “you” asked about changing the “Only Accept SIP Requests From Known Servers” setting due to a combination with STUN. Using this I dug into the user manual and found the setting at "Account -> Account Settings / Account 1 Selection -> Advanced Settings Tab -> Security Settings Section -> “Only Accept SIP Requests from Known Servers”, which was checked in previous firmwares (back to and is checked now, but when unchecked, the SIP Speaker does resume registration immediately after setting application. HOWEVER, this setting/fix does NOT persist when the SIP Speaker is restarted.

If you could please advise on a permanent fix or on any further information, it will be greatly appreciated. Thank you and have a great day!