Technical Tip: FortiGate is not responding to SNMP queries

[AndrewX]

Description	This article describes the issue when FortiGate is not responding to SNMP queries.
Scope	FortiGate v7.4.x.
Solution	Possible Reason 1: Background information: The Cisco Switch can communicate with the SNMP server via the IPSec tunnel correctly, whereas FortiGate cannot respond to SNMP server queries via the IPSec tunnel. Network diagram:   Cisco SW---FGT100F-----IPSec VPN------ SNMP server. The packet sniffer shows that the traffic comes in, but there is no return traffic.                                  Verify that the Routing configuration and firewall policy are all set up properly, as it is possible to see from the source IP in FortiGate that it can ping and traceroute to the SNMP server.                              Checked the local policy which allowed the source to the SNMP server. Run the debug to capture the SNMP information; however, nothing is shown on the debug.                                   Solution: Add the SNMP server IP as a trusted host under the local admin account, and then it will start working. Possible Reason 2: Unable to match the SNMP community on the FortiGate due to a case-sensitive community name  The SNMP community name specified on the SNMP manager is 'public'. The SNMP community name specified on the FortiGate is 'Public'. config system snmp community     edit 2         set name "Public" <---         set status enable      next end The FortiGate will not reply to the SNMP traffic coming from the SNMP manager, as the community's name does not match, as it is case-sensitive. Run the snmpd debugs: diagnose debug reset diagnose debug application snmp -1 diagnose debug enable Below debugs are expected: snmpd: checking if community 'public' is valid. snmpd: failed to match community 'public'. Solution: Make sure the community's name is identical on both the SNMP manager and the FortiGate. Possible Reason 3: Make sure that the SNMP agent is enabled. Solution: The SNMP agent must be enabled to support SNMP configuration. This ensures the system can generate SNMP traps and respond to SNMP queries from the management server.