Created on
09-09-2024
12:10 AM
Edited on
03-12-2025
06:42 AM
By
Jean-Philippe_P
Description | This article describes that if the FortiGate is acting as a DHCP-relay and if the switch is the downstream device, it is possible to encounter the error 'can't get server id from client message'. The reason is that the PC not getting an IP address. |
Scope | FortiGate. |
Solution |
Topology: PC---------Switch1(vlan451)----------Switch2-----------Port 11 - Fortigate Relay- Port 10 ---------DHCP Server.
diagnose debug application dhcprelay -1 If it is happening, the following error 'Warning! can't get server id from client message' in debugs appear. Make sure in the switch, the DHCP relay is disabled.
Note: This error does not necessarily mean that the issue is with the DHCP relay on the switch. Make sure that the DISCOVER packets are forwarded to the DHCP server and are visible in the pcap on the relay server.
To isolate one trace and analyze the report the 'xid' can be taken (e.g.,xid:b3ed0683) in the following way:
2025-02-20 12:05:57 (xid:b3ed0683) received request message from 0.0.0.0:68 to 255.255.255.255 at VLAN-34
More troubleshooting should be performed such as :
To get the packet capture in FortiGate GUI, the following KB article Troubleshooting Tip: Packet Capture on FortiOS GUI can be followed. Filter ports 67 and 68.
diagnose sniffer packet <interface> "port 67 or port 68" 6 0 l
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