MX DHCP Issues

[Jess65065]

We have been having this issue for a while. Meraki has not provided a solution. Our MX device stops responding to DHCP requests. The pool is nowhere near maxed out. We have downgraded and replaced the MX, but nothing helps. We checked the device utilization to see if it was working too hard but it's only at 25%. We can't figure out why the DHCP function just stops. The only fix has been to reboot the firewall to start DHCP backup. 

[Cisco_Virtual_Engineer]

The DHCP service on a Meraki MX device may stop responding to requests due to several reasons:

1. Misconfiguration: The DHCP service may stop responding if there are misconfigured settings on the MX device. This could include incorrect client addressing, lease times, DNS nameservers, or boot options. It is important to ensure that the DHCP configuration is accurate and matches the requirements of the network.

2. Resource Exhaustion: If the MX device is experiencing high resource usage, such as high CPU or memory utilization, it may not be able to handle DHCP requests effectively, leading to unresponsiveness. In such cases, it is recommended to check the resource utilization of the device and take appropriate actions to resolve any resource constraints.

3. Network Connectivity Issues: DHCP requests may fail if there are network connectivity issues between the MX device and the DHCP clients or DHCP server. This could be due to physical connectivity problems, routing issues, or firewall rules blocking DHCP traffic. It is essential to perform network troubleshooting to identify and fix any connectivity problems.

4. DHCP Relay Configuration: If the MX device is configured to relay DHCP requests to another DHCP server, there may be issues with the DHCP relay configuration. This could include incorrect relay server IP address or the relay agent using the incorrect source port. It is important to verify the DHCP relay configuration and ensure it is correctly set up.

To diagnose and resolve the issue, you can perform the following troubleshooting steps:

1. Check the DHCP configuration on the MX device and ensure that all settings are properly configured. Verify the client addressing, lease times, DNS nameservers, and boot options.

2. Monitor the resource utilization of the MX device using the live monitoring features. Check for high CPU, memory, or network utilization that could impact DHCP service performance.

3. Perform network connectivity tests between the MX device and the DHCP clients/server. Ensure there are no physical connectivity issues, routing problems, or firewall rules blocking DHCP traffic.

4. Verify the DHCP relay configuration, if applicable. Ensure the relay server IP address is correct and the relay agent is not using port 68 as the source port.

If none of these steps resolve the issue, it is recommended to reach out to Cisco Meraki support for further assistance in troubleshooting and resolving the DHCP service unresponsiveness.

[Jess65065 · Accepted solution]

Sorry AI bot, most of your points were addressed in my original post. Weirdly what has helped is removing all layer 7 firewall rules even though utilization never got above 25% according to the MX. We have not had a DHCP issue since removing the layer 7 rules. We will be switching vendors. If it stops responding to DHCP requests because it cant handle blocking facebook that is crazy and useless.