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Below is port1 configured as a DHCP-enabled WAN interface. An attempt is made to get an IP address from the upstream ISP router/modem.
config system interface
edit "port1"
set vdom "root"
set mode dhcp
set allowaccess ping ssh https
set role wan
set snmp-index 1
set type physical
end
Execute the following debug commands:
diagnose debug application dhcpc -1
diagnose debug console timestamp enable
diagnose debug enable
The following output will be generated if the interface does not get an IP:
DHO_BROADCAST_ADDRESS option is missed
DHCPOFFER received on port1
client Xid:0x126C8F83 in state:2, pkt Xid:0xADF13443
DHCPOFFER in wrong transaction.
timer 0x8d51b20(state_panic -> state_init) will expire in 11 secs
timer 0x8d51b20(state_panic -> state_init) will expire in 10 secs
timer 0x8d51b20(state_panic -> state_init) will expire in 9 secs
timer 0x8d51b20(state_panic -> state_init) will expire in 8 secs
timer 0x8d51b20(state_panic -> state_init) will expire in 7 secs
timer 0x8d51b20(state_panic -> state_init) will expire in 6 secs
timer 0x8d51b20(state_panic -> state_init) will expire in 5 secs
A 'DHCPOFFER in the wrong transaction' error occurs when a DHCP client receives a DHCPOFFER message with a transaction ID that does not match the one it used in its DHCPDISCOVER request. This indicates that the offer is not part of the client's current DHCP session.
The DHCP client typically accepts the first valid DHCP offer it receives
This can happen due to:
- Multiple DHCP servers operating within the same broadcast domain result in unsolicited or conflicting responses.
- Misconfigured DHCP servers respond incorrectly to discovery messages.
- Delayed or residual DHCP packets from previous transactions are being received and processed out of sequence.
These conditions can lead to IP address conflicts, assignment failures, or network instability, especially in environments with overlapping scopes or improper network segmentation.
Try restarting dhcp process on FortiGate using the following command:
fnsysctl killall dhcpd
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