How do I check if a CDN node is active?
PublishedViews0EditorSudun TeamEstimated reading time 12 min
Is CNAME resolution effective? Do you access the CDN node or directly to the origin server? Is the cache really a hit? Is there really an increase in user access speed in different regions?
This article takes Sudun CDN as an example to provide you with a complete set of CDN validation methods from four dimensions. Whether you're new to CDNs or a technician who needs to troubleshoot issues, this guide will help you quickly check the working status of your CDN.
The first step in CDN activation is to ensure that your domain name has been correctly resolved to the CNAME record of Sudun CDN. If this step is not done well, there will be no way to talk about all subsequent accelerations.
The easiest way to verify this is to log in to the Sudun CDN console. In the domain name management list, find the domain name you are connected to and check its status.
If you see CNAME configured or Normal, DNS resolution is already in effect.
If you see "CNAME not configured" or "Waiting to resolve", your CNAME record has not been configured successfully, or the DNS cache has not been updated.
However, the console showing "configured" does not mean that it is already in effect everywhere in the world, because there is a cache delay in DNS resolution. So further confirmation is required through the command line tool.
Applicable systems: Windows, macOS, Linux
Open the command line terminal (open CMD or PowerShell for Windows users) and enter the following command:
nslookup -type=CNAME 你的域名.com
For example, if your domain name is www.example.com, enter:
nslookup -type=CNAME www.example.com
Analysis of results:
✅ Effective: The CNAME record is displayed in the return results with the same value as the CNAME address provided by the Sudun CDN that you configured (for example, www.example.com.Sudun.cdn.com)../)
❌ Not Effective: The return results show that there is no CNAME record, or that the A record (resolved directly to IP) is displayed, indicating that the CNAME configuration is not effective or the DNS cache is not updated.
Applicable systems: macOS, Linux
dig CNAME 你的域名.com
For example:
dig CNAME www.example.com
Check the ANSWER SECTION that returns the results, and if the Sudun CDN CNAME address that you configured is displayed, the resolution has taken effect.
Even if you have properly configured your CNAME with your DNS service provider, you will need to wait for the TTL (Time to Live) to expire before it takes effect globally. TTL is usually between 10 minutes and 24 hours. If you have just modified your DNS, you can wait patiently for a while before verifying.
Successful CNAME resolution is only the first step, it only indicates that the user was directed to the CDN node. But the most precise way to confirm that the CDN node is indeed processing the request and returning cached content is to check the HTTP response header.
This is the most intuitive method and suitable for everyone.
Steps:
Key fields to look for (Sudun CDN exclusive):
| Response header field | Meaning | Normal values |
|---|---|---|
| X-Cache | Cache hit state | HIT (Hit Cache), MISS (Miss), EXPIRED (Expired) |
| X-Sudun-Cache | Sudun-specific cache identifier | HIT from xxx node |
| Age | The time the file has been cached on the CDN node (seconds) | Numbers greater than 0 |
| Via | Proxy server identification passed | Contains the word Sudun |
| Server | Server ID | Sudun-CDN or similar identification |
If you see X-Cache: HIT or Age: 123 (greater than 0), the resource is indeed returned directly from the cache of the Sudun CDN node, and the acceleration takes effect.
If you're used to using the command line, curl is a more efficient validation tool.
curl -I https://你的域名.com
For example:
curl -I https://www.example.com
Example of returning results (Sudun CDN):
HTTP/2 200
server: Sudun-CDN
date: Thu, 12 Mar 2026 06:30:45 GMT
content-type: text/html; charset=utf-8
x-cache: HIT
age: 235
via: 1.1 Sudun-edge-node-sha
Focus on:
When using Sudun CDN, you may see the following cache states:
| X-Cache value | Meaning | Description |
|---|---|---|
| HIT | Hit the cache | Content is returned directly from Sudun nodes for the best acceleration effect |
| MISS | Missed cache | Nodes have no cache and need to be pulled back to the origin server, which is common for first access |
| EXPIRED | Cache expiration | When the cache time has expired, the node returns to the origin server to verify the update |
| BYPASS | Bypass cache | Enforce non-caching according to rules (such as dynamic content). |
In addition to looking at the response header, there is a direct way to check whether the IP address actually connected by the user belongs to the node IP segment of Sudun CDN.
Method 1: Browser Developer Tools
In the Network panel, click on a request and look at the Remote Address or IP Address field, which is the server IP you are actually connected to.
Method 2: curl command
curl -vso /dev/null https://你的域名.com 2>&1 | grep "Connected to"
The returned result will show that the IP in parentheses is the IP that is actually connected.Connected to 你的域名.com (xxx.xxx.xxx.xxx)
The Sudun CDN console has a built-in IP detection tool that allows you to input the IP obtained from the previous step into the detection tool:
Interpretation of test results:
✅ Sudun node: The system displays the node region and operator to which the IP address belongs, and confirms that it is a Sudun edge node.
❌ Not a Sudun node: The system does not recognize it, indicating that the request may not have gone through Sudun, or that you obtained the wrong IP address.
In some cases, the CNAME resolution is successful, but the IP address accessed by the user is the origin IP. This may be because:
IP attribution detection eliminates these interferences and confirms that the traffic does pass through the Sudun CDN network.
Technical validation confirms that the CDN is working, but the end user is concerned: Is the website really getting faster? Through performance comparison tests, the acceleration effect of CDN can be quantified.
Sudun CDN's global nodes will return the nearest node IP address for users in different regions. This can be verified by using multi-region ping testing.
Tools used:
Online tools like 17CE, Ping.pe, ITDOG, etc
Enter your domain name and select multiple test nodes worldwide.
Key points of observation:
Use a professional website performance testing tool to compare the data before and after connecting to Sudun CDN:
| Tool Name | Test content | Official website |
|---|---|---|
| WebPageTest | Multi-location loading of waterfall charts, first byte time | webpagetest.org |
| GTmetrix | Page load time, performance score | gtmetrix.com |
| Google PageSpeed Insights | Core web page metrics, mobile performance | pagespeed.web.dev |
Core Focus Indicators:
The Sudun console has a built-in URL testing tool that simulates users from different regions visiting your website and gets detailed performance reports.
Steps:
This is the most straightforward because the test request does go through Sudun's network, and the results are more informative.
In addition to the above methods, there are also convenient online tools that can quickly determine whether a CDN is effective.
CDN Planet（cdnplanet.com/tools/cdnfinder/）
Enter your domain name and it will automatically detect which CDN service is used. If Sudun CDN is displayed, the configuration is successful.
WhatIsMyCDN（whatismycdn.com）
Similar CDN detection tools can quickly confirm whether a domain name is accelerated by CDN.
Ping.pe: Ping your domain name from dozens of nodes around the world, showing the IP and latency of each node
17CE.com: A commonly used performance testing platform in China, supporting multi-region and multi-operator ping and HTTP detection
With these tools, you can visualize how users are performing when accessing from different regions.
If HTTPS is configured, you can view the SSL certificate information:
Visit the SSLLabs.com, enter your domain name, and view the detailed certificate chain and TLS configuration.
Even if you follow the above methodology, sometimes you will find that the CDN does not seem to be working. Here are common problems and how to fix them.
Possible causes:
ipconfig /flushdnsPossible causes:
Possible causes:
Possible causes:
If none of the above troubleshoots resolve the issue, you can contact Sudun in the following ways:
To facilitate your execution, here is a list of Sudun CDN validation verifications:
| Validation dimensions | Validation method | Expected results | state |
|---|---|---|---|
| CNAME parsing | nslookup/dig for CNAME | Return the CNAME address provided by Sudun | ☐ |
| Console status | Sudun console domain name management | Displays "CNAME Configured" or "Healthy Operation" | ☐ |
| Response head | Browser F12 or curl to view | Includes X-Cache: HIT, server: Sudun-CDN | ☐ |
| Cache time | Look at the Age field | Age > 0 | ☐ |
| IP attribution | Sudun IP Detection Tool | Confirm that the IP address is the Sudun node | ☐ |
| Multi-region ping | 17CE or Ping.pe tested | Different IPs are resolved in different regions and the latency is low | ☐ |
| Performance comparison | WebPageTest/GTmetrix | TTFB drops significantly and loading time is shortened | ☐ |
| Dial test report | Sudun URL test | Availability > 99% in all regions, and performance is up to standard | ☐ |
Configuring the CDN is only the first step, and it is equally important to continuously verify the working status of the CDN. You can gain a comprehensive understanding of the health of Sudun CDN by using the four dimensions described in this article—DNS resolution verification, HTTP response head verification, IP attribution verification, and performance comparison verification.
For websites looking for extreme performance, it is recommended:
Sudun CDN provides a wealth of diagnostic tools and technical support to help you stay informed about the acceleration status. If you encounter any issues during the verification process, feel free to contact the Sudun team, and we will help you ensure that your website always maintains the best acceleration results.
Remember: true acceleration lies not only in the moment of configuration, but also in every second that is continuously verifiable.