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Version: v25.07.31

DNS Troubleshooting

This document outlines the steps required to troubleshoot DNS resolution issues on CE (Customer Edge) devices. It covers accessing the terminal, examining configuration files, verifying network settings, and monitoring system logs.

Troubleshooting steps​

Cloud Configuration Verification​

Access the CE Terminal​

Before starting the troubleshooting process, ensure the necessary permissions are in place to run the commands. To do this, run the following command.

sudo su -

Verify the Last Applied Configuration​

This command is used to view information about the last successfully applied DNS configuration. Here, this command is used to retrieve the DNS server settings information and help identify the problem from the stored configuration response JSON file.

cat /tmp/last_config_response.json | jq '.service.dns'

This command will display the contents of the /tmp/last_config_response.json file. Carefully inspect the output and look for DNS server IP addresses or errors.

The configuration done on the cloud will be shown here. The output provided here is only for example purposes and displays the currently applied configuration

The given one is just an example output; when this command is run, it will show something like this.

Example Result:​


{
  "cacheSize": 8000,
  "disable": false,
  "listenAddress": [
    "0.0.0.0"
  ],
  "listenOn": [],
  "domains": [],
  "nameserver": [
    "117.186.234.100",
    "103.78.41.247"
  ],
  "allowFrom": [
    {
      "address": "0.0.0.0",
      "netmask": "0.0.0.0",
      "cidrSignature": "0.0.0.0/0",
      "subnet": "0.0.0.0"
    }
  ]
}

In the example above, nameserver shows the configured DNS server IP addresses.

Q:1 Does this command show real-time changes in the cloud?

No. The command: cat /tmp/last_config_response.json | jq '.service.dns'. does not show real-time changes in the cloud. Instead, it displays the last successfully applied DNS configuration that was stored locally on the CE device. It reflects the configuration pushed from the cloud at the time of the last update. Any new changes made in the cloud will only appear here after they have been applied and synced to the device. This makes it useful for verifying what configuration is currently active, but not for monitoring live updates

Q:2 Which command should be used to verify the last applied configuration?

To verify the last applied DNS configuration, use: cat /tmp/last_config_response.json | jq '.service.dns'. This command reads the JSON file /tmp/last_config_response.json and filters the DNS section. It shows details such as cache size, listen address, nameservers, and allowed sources. Reviewing this output helps confirm whether the DNS settings were applied correctly and highlights any misconfigurations.