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Cisco Meraki Documentation

Troubleshooting Meraki AP DHCP and DNS Issues

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Overview 

This article explains how to troubleshoot common DHCP and DNS issues that affect Cisco Meraki access points (APs). It provides step-by-step guidance to diagnose and resolve problems that prevent APs from contacting the Meraki Cloud or prevent clients from receiving a DHCP lease, aiming to minimize downtime and improve user experience. 

Environment 

  • Meraki access points (gateway APs) 

  • DHCP server (on the wired LAN) 

  • DNS server 

Troubleshooting DHCP option misconfiguration issue 

Gateway APs report the following alerts: 

  • Alert: This device is having difficulty contacting the Meraki Cloud 

  • This gateway is disabled. Its Domain Name Service (DNS) configuration is not working 

Possible causes 

  • The DHCP server is incorrectly configured to use DHCP Option 5 "Name Servers" This option is for setting Internet name servers and is not supported.  

  • Meraki access points support DHCP Option 6 Domain Name Servers.  

Troubleshooting steps 

  1. Review your DHCP server configuration. 

  1. Check if the DHCP server is using DHCP Option 5 "Name Servers," which Meraki APs do not support. 

  1. If so, switch your configuration to DHCP Option 6 "DNS Servers" to supply DNS server information to Meraki APs. 

  1. Refer to your DHCP server setup guide for assistance with configuring DHCP options. 

Expected outcome 

The gateway AP successfully receives a valid DNS configuration, contacts the Meraki Cloud, and is no longer disabled. 

 

Troubleshooting DHCP "no_offers_received" issue 

When Bridge mode is enabled, wireless and wired clients connected to Meraki APs receive an IP address from the DHCP server on the wired LAN.  

If clients cannot receive a DHCP lease, you may see a similar message in the Meraki Event log: 

Dec 29 14:01:58 MYCOMPUTER DHCP problem AP1 meraki vlan 0, extra no_offers_received  

When the MX receives 3 DHCP Discovers from the same client in a 5-minute window, it also triggers this event log entry. 

Possible causes 

  • The DHCP server is offline or not operational. 

  • DHCP server is configured incorrectly. 

  • The DHCP address pool has no available IP addresses left. 

Troubleshooting steps 

  1. Confirm your DHCP server is online, operational, and configured correctly with an active DHCP scope. 
  2. Check whether you have exhausted all available IP addresses in your DHCP address pool. Increase the size of the DHCP address pool if needed. 
  3. If the DHCP scope for your local LAN is configured on a DHCP server in a different broadcast domain, confirm you have an IP helper or a DHCP relay agent configured on the local LAN to intercept DHCP discovery broadcasts and forward them to the appropriate DHCP server. 
  4. If you use a DHCP reservation, confirm the IP address assigned to your potential client's MAC address is part of your DHCP address pool and not excluded. 
  5. Confirm DHCP Discovers reach your DHCP server successfully. 

Expected outcome 

Clients successfully receive a DHCP lease, and the "no_offers_received" message no longer appears in the Meraki Event log. 

Troubleshooting DNS misconfiguration issue (Linksys WRT54GS) 

A “DNS misconfiguration” alert appears on Cisco Meraki APs when used with a Linksys WRT54GS device. 

Possible causes 

  • The Linksys DHCP service supplies DHCP clients with the same DNS server IP addresses it maintains on its WAN interface. 

Troubleshooting steps 

  1. Try changing the DNS servers on the WAN interface. Test if it reflects correctly on the LAN side DHCP service.  

  1. If the issue persists, updgrade the Lynksys WRT54GS firmware to version 7.2.08 or later. After the firmware update, reboot the Cisco Meraki AP.