Chapter 10 Install and System Administration for FortiOS 5.0 : Monitoring : SNMP : Enabling on the interface
  
Enabling on the interface
Before a remote SNMP manager can connect to the FortiGate agent, you must configure one or more FortiGate interfaces to accept SNMP connections.
To configure SNMP access - web-based manager
1. Go to System > Network > Interface.
2. Choose an interface that an SNMP manager connects to and select Edit.
3. In Administrative Access, select SNMP.
4. Select OK.
To configure SNMP access - CLI
config system interface
edit <interface_name>
set allowaccess snmp
end
 
If the interface you are configuring already has protocols that are allowed access, use the command append allowaccess snmp instead, or else the other protocols will be replaced. For more information, see “Adding and removing options from lists”.
See Also
SNMP configuration settings
Gigabit interfaces
SNMP agent
SNMP community
Fortinet MIBs
SNMP get command syntax