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Dynamic DNS (DDNS)

Overview

The Cisco Meraki MX Security Appliance uses Dynamic DNS (DDNS) to update its DNS host record automatically each time its public IP address changes. This feature is useful because it allows the administrator to configure applications such as client VPN to access the MX by its hostname which is static instead of an IP address that may change over time. 

Configuration 

 

1. To use Dynamic DNS on your MX Security Appliance, it must first be set to NAT mode. This is done under Security Appliance > Configure > Addressing and VLANs in Dashboard.

Enabling NAT Mode

2. Once the MX is set to NAT mode, the Dynamic DNS section will appear under Security Appliance > Configure > Addressing & VLANs. Set the Automatic registration drop down to enabled and specify a hostname in the Public domain name field. The dynamic dns name for each uplink will appear at the bottom of the page. 

Enabling Dynamic DNS

 


 

3. After Dynamic DNS is enabled, you can confirm it is working by performing a DNS query for the MX DNS hostname.  Open a command prompt on any workstation and type "nslookup <your dynamic DNS name>." The DNS response should return the current active public IP address of the MX.  

 

Note: The expected TTL for dynamic DNS records is typically about 10 minutes.

Troubleshooting

Querying the MX DNS hostname

Testing Dynamic DNS Resolution 

The following instructions describe how to find out what servers are resolving our dynamic DNS, and query them to see what IP address they are associating to the MX:

  1. Open cmd.exe from "C:\Windows\System32" on your laptop, and run a "nslookup"

cmd1.png

  1. Set query to any and sort it for the dynamic-m.com. It will list all the servers used by the dynamic.com. 

cmd2.png

  1. This lists the servers serving this dynamic-m site for its host names look-up. You would be checking if you could search for the host-name from the individual servers.

nslookup [-option] [hostname] [server]

cmd3.png

This would help in learning if the IP address was ever updated on the server and if the problem is with grabber executable file or the servers not responding to the requests.

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ID: 1482

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