CDN:Check if an IP address is a CDN POP

Prerequisites

• An accelerated domain name added to Alibaba Cloud CDN

• DNS resolution for the domain name pointing to the CNAME address assigned by Alibaba Cloud CDN

• curl or an equivalent HTTP client installed on your machine

Step 1: Obtain the IP address to check

Obtain the IP address that clients connect to when they access your accelerated domain name.

Run the following command:

# Replace <your accelerated domain name> with your actual accelerated domain name
curl -vso /dev/null https://<your accelerated domain name> 2>&1 | grep "Connected to"

The output shows the IP address that the client connected to. Use this IP address in the next step.

Step 2: Use the IP address check tool

• Both IPv4 and IPv6 addresses are supported.

• You can check up to 20 IP addresses at a time.

Step 3: Check HTTP response headers for CDN cache status

In addition to using the IP Address Check tool, you can check HTTP response headers to determine whether a request passed through Alibaba Cloud CDN and whether it hit the CDN cache.

Run the following command to view the HTTP response headers for your accelerated domain name:

# Replace <your accelerated domain name> with your actual accelerated domain name
curl -I https://<your accelerated domain name>

In the response headers, check the following fields:

• X-Cache: Indicates the CDN cache status.

  • HIT: The request hit the CDN cache. The resource was served directly from the CDN POP without a back-to-origin request.

  • MISS: The request missed the CDN cache. The CDN POP sent a back-to-origin request to retrieve the resource from the origin server.

• Via: Indicates the intermediate proxy nodes through which the request was routed. If this field contains a CDN POP identifier such as cache, the request was processed by a CDN POP.

Example response headers:

HTTP/2 200
x-cache: HIT TCP_MEM_HIT
via: cache21.l2cn3000[146,0], cache10.cn3000[1,0]

In this example, the X-Cache value of HIT indicates a cache hit, and the cache identifier in the Via field confirms that the request was routed through a CDN POP.

Result analysis