When you enable failover of the DHCP server, some clients cannot obtain IP addresses

Question

Currently, there are two DHCP server servers, and after configuring the failover function of DHCP, some terminal devices cannot obtain IP addresses, but after the failover function is disabled, the address can be obtained. Packet capture finds that the server does not have DHCP packets.

Answer 1

Hello,

If you have configured the failover function for DHCP and some terminal devices are unable to obtain IP addresses, it could indicate an issue with the failover configuration. Here are a few troubleshooting steps you can follow to investigate the problem:

Check DHCP server status: Verify that both DHCP servers are running and operational. Ensure that the DHCP service is started on both servers and there are no errors or warnings in the DHCP server logs.

Verify failover configuration: Double-check the failover configuration settings on both DHCP servers. Ensure that the failover relationship is correctly established and synchronized between the servers. Pay attention to settings such as mode (load balance or hot standby), relationship name, partner server IP address, and shared secret.

Review DHCP lease pool: Check the DHCP lease pool configuration on both servers. Ensure that the lease duration and available IP address range are correctly configured. Make sure that the pool has enough available addresses to accommodate all the DHCP clients.

Examine packet capture results: If the server is not receiving DHCP packets, capture network traffic on both DHCP servers using a tool like Wireshark. Filter the capture for DHCP traffic (UDP port 67 and 68) and analyze the results. Look for any anomalies, missing packets, or error messages that could indicate communication issues.

Check network connectivity: Confirm that there is proper network connectivity between the DHCP servers and the affected terminal devices. Ensure that there are no network configuration issues, such as incorrect VLAN settings or firewall rules blocking DHCP traffic.

Validate firewall settings: If you have firewalls or security appliances between the DHCP servers and the terminal devices, ensure that they are not blocking DHCP packets. Review the firewall rules to allow DHCP traffic (UDP ports 67 and 68) between the servers and the clients.

Test failover behavior: Temporarily disable the failover function and check if all terminal devices can obtain IP addresses successfully. This step will help determine if the issue is specific to the failover configuration or if there are other underlying problems.

Verify DHCP client configuration: Ensure that the affected terminal devices are configured to obtain IP addresses automatically via DHCP. Double-check the network adapter settings on the devices to confirm that they are set to obtain an IP address automatically.

Monitor DHCP server logs: Continuously monitor the DHCP server logs on both servers while attempting to obtain IP addresses on the affected terminal devices. Look for any relevant error or warning messages that could provide insights into the problem.

If the issue persists and you are unable to identify the root cause, it might be helpful to consult with your network administrator or seek assistance from the technical support channels provided by your DHCP server vendor.

I used AI provided by ChatGPT to formulate part of this response. I have verified that the information is accurate before sharing it with you.

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