Description
This article describes how to check why SSL VPN connections are not possible.
This, when triggered, leaves the following traces in the crashlog:
diagnose debug crashlog read
Output example:
2010-11-02 20:09:22 SSL VPN enter conserve mode.
The typical behavior: No SSL VPN Web portal connections are accepted. Users get the '503 Service Temporarily Unavailable' error.
Scope
FortiGate.
Solution
SSL VPN in FortiOS has its own Conserve Mode, which is triggered before the regular system conserve mode. This is caused by MEM tension on the system.
Troubleshooting steps:
Run the following command:
diag sys top-summary
As of version 7.2.x and above, the following command can be used:
diag sys top-mem
If the Firewall is in VDOM mode, make sure to change to the VDOM.
Fortigate # diag vpn ssl statistics
SSLVPN statistics (root):
------------------
Memory unit: 1
System total memory: 2111090688
System free memory: 1140170752
SSLVPN memory margin: 314572800
SSLVPN state: conserve
Max number of users: 1
Max number of tunnels: 0
Max number of connections: 6
Current number of users: 0
Current number of tunnels: 0
Current number of connections: 0
Solution: Adjust metrics like (UTM profiles, Traffic shaping, Logging or any process that is using large amounts of memory etc.) to reduce the MEM and Memory consumption of the FortiGate firewall.
Related documents:
The Fortinet Security Fabric brings together the concepts of convergence and consolidation to provide comprehensive cybersecurity protection for all users, devices, and applications and across all network edges.
Copyright 2025 Fortinet, Inc. All Rights Reserved.