IC Knowledge Base

Fortigate SSL/TLS Handshake fails

In some circumstances when using WiFi clients browsing to SSL/TLS server hosts you will see "TLS timeout" or "TLS handshake error"


This can be caused by setting the WiFi interface on the fortigate to default (1500) As the WiFi encryption overhead coupled with the IPSec overhead AND the SSL/TLS bits needed the MTU will be exceeded

Set the WiFi Interface as follows


con sys int 

edit "interface name"

set mtu-override enable

set mtu 9000




0 (0)
Article Rating (No Votes)
Rate this article
Attached Files
There are no attachments for this article.
There are no comments for this article. Be the first to post a comment.
Security Code Security Code
Related Articles RSS Feed
Technical Note: DNS resolution not working when DNS Server configured to ’Same as Interface IP’
Viewed 7882 times since Wed, Aug 9, 2017
Fortigate DC Replication RPC port 135 Session-Helper
Viewed 5008 times since Wed, Dec 6, 2017
How to configure DNS based FortiGuard web filtering with FortiOS v5.4
Viewed 5337 times since Wed, Aug 2, 2017
Technical Note: Error ’Unable to establish the VPN connection. The VPN server may be unreachable. (-5)’ on FortiClient with SSL VPN
Viewed 40137 times since Mon, Aug 7, 2017
FortiGate MAC host check on SSL VPN
Viewed 6000 times since Fri, Aug 31, 2018
Technical Note: Custom NTP server configuration
Viewed 3343 times since Fri, Aug 11, 2017
Full (Deep) SSL Inspection - Avoid certificate errors
Viewed 5755 times since Thu, Jul 26, 2018
Fortigate Hairpin NAT
Viewed 8794 times since Fri, Aug 4, 2017
Fortigate Phase 2 Keep Alive
Viewed 2281 times since Thu, Jul 26, 2018
Internet Central Limited, Innovation Centre, Keele Science Park, Keele, Staffordshire ST5 5NB
Registered Office: Ivy House Foundry, Hanley, Stoke-on-Trent, ST1 3NR
Registered in England: Reg No. 03079542 VAT Reg No. GB 278 923 705
Contact Us |Terms & Conditions |Legal, Privacy and Cookies
All prices exclude VAT E.&O.E © 2015 Internet Central

All trademarks and logos appearing on the site are the property of their respective owners