Troubleshooting Tip: DHCP debug message 'There is no requesting IP in subnet!'

[nithincs]

Description	This article describes the background of DHCP message exchange and explains the root cause of the DHCP debug message 'There is no requesting IP in subnet!'
Scope	FortiGate.
Solution	While debugging the DHCP service running in the firewall, it is necessary to run the 'dhcps' debug commands. dia de reset dia de console timestamp enable dia de app dhcps -1 dia de enable To stop the debug: dia de reset dia de disable Upon running the debug, the dhcp daemon debug output can be seen when FortiGate receives any DORA Discover, Offer, Request, Acknowledgement) message exchanges between FortiGate and the client. The debug also shows if there are any errors during the DORA process. The following output can be seen when FortiGate receives a DHCPDISCOVER message: 2023-06-14 05:00:08 [note]DHCPDISCOVER from 00:50:79:66:68:09 via port2(ethernet) 2023-06-14 05:00:08 [debug]There is no requesting IP in subnet! 2023-06-14 05:00:09 [debug]locate_network prhtype(1) pihtype(1) 2023-06-14 05:00:09 [debug]find_lease(): leaving function WITHOUT a lease This debug output is observed when all IP addresses in a DHCP IP range are assigned and there is no IP address available to assign to a new client. Note: Each reserved-address is considered as a leased IP. In these conditions, FortiGate will not send the offer message and will ignore the DHCPDISCOVER message. To resolve this situation, increase the ip-range limit based on the total DHCP clients in the network. Minimize the lease time to help in clearing leased IP entries in fortigate if the DHCP client system is in sleep mode, shut down, or is otherwise not active in the network. Example: DHCP config: config system dhcp server edit 2 set dns-service default set default-gateway 10.0.0.1 set netmask 255.255.255.248 set interface "port2" config ip-range <-- FortiGate can provide IPs to 5 clients. edit 1 set start-ip 10.0.0.2 set end-ip 10.0.0.6 next end config reserved-address <-- 4 are reserved. edit 1 set ip 10.0.0.2 set mac 74:78:27:9d:48:bf next edit 2 set ip 10.0.0.3 set mac 74:78:27:9d:48:a1 next edit 3 set ip 10.0.0.4 set mac 74:11:27:9d:48:bf next edit 4 set ip 10.0.0.5 set mac 00:78:27:9d:48:bf next end next end GUI: At this point, FortiGate can assign an IP address to a single client. exe dhcp lease-list port2 IP MAC-Address Hostname VCI SSID AP SERVER-ID Expiry 10.0.0.6 50:ff:f3:00:07:00 UNL MSFT 5.0 2 Wed Jun 21 04:57:58 2023 The DHCPDISCOVER request comes from 00:50:79:66:68:09 and FortiGate is out of IP addresses. DHCP debug will show the output 'There is no requesting IP in subnet!' 2023-06-14 05:00:08 [note]DHCPDISCOVER from 00:50:79:66:68:09 via port2(ethernet) 2023-06-14 05:00:08 [debug]There is no requesting IP in subnet! 2023-06-14 05:00:09 [debug]locate_network prhtype(1) pihtype(1) 2023-06-14 05:00:09 [debug]find_lease(): leaving function WITHOUT a lease