FortiGate Next Generation Firewall utilizes purpose-built security processors and threat intelligence security services from FortiGuard labs to deliver top-rated protection and high performance, including encrypted traffic.
This article describes how to resolve an issue where FSSO CA stops sending new logged on users with a debug error message 'packet size too big'.
Scope
FortiGate configured with FSSO. The FSSO user filter is configured on the FortiGate (Local FSSO filter).
Solution
The cause of this issue is usually a high number of selected induvial users and user groups in the FortiGate local FSSO filter.
FSSO collector agent logs:
12/23/2025 00:04:48 [ 5740] FortiGate connection accepted, no auth check. 12/23/2025 00:04:48 [ 5740] FortiGate:FGXXXXXXXXXXXXXX-root connected on socket (4852). 12/23/2025 00:04:48 [ 5740] send AUTH, len:26 12/23/2025 00:04:48 [ 5740] ready to read from socket 12/23/2025 00:04:48 [ 5740] packet size too big:1073804 12/23/2025 00:04:48 [ 5740] reset connection 0
To resolve this issue, unnecessary users/groups must be deselected from the filter. Only users/groups that will have a firewall policy reference should be selected.
