Technical Tip: Monitor DHCP via SNMP

[Rosalyn]

Description

This article describes how to monitor DHCP via SNMP.

Scope

FortiGate.

Solution

SNMP will monitor DHCP and send out traps when:

• DHCP server IP pool usage hits 90%.
• The DHCP server detects an IP address which already used by an end unit.
• DHCP client receives DHCP NAK,
  
  

SNMP queries refer to DHCP lease usage information (OID = 1.3.6.1.4.1.12356.101.23.2.1.1.2).

See the FortiGate DHCP MIBs - FortiGate 7.6.0 documentation.

The query result is based on the leased out percentage.

To enable the SNMP DHCP event in the GUI:

1. Go to System -> SNMP.
2. Select 'Create New' in either the SNMP v1/v2c table or SNMP v3 table, or edit an existing community or user.
3. Configure the settings as required.
   
   

In the SNMP Events list, enable 'snmp-event::dhcp'.

To enable the SNMP DHCP event in the CLI:

config system snmp community
    edit 1
        set name "test-sys"
            config hosts
                edit 1
                    set ip 10.10.10.1 255.255.255.255
                next
            end
        set events dhcp
    next
end

config system snmp user
    edit "test"
        set notify-hosts 10.47.1.237
        set events dhcp
        set security-level auth-priv
        set auth-proto sha224
        set auth-pwd xxxxxx
        set priv-pwd xxxxxx
    next
end