How to identify POP of CDN provider?

We have all heard how it is a good idea to use a CDN for serving static assets, but how does one go about identifying, from which POP are the resources being served from i.e. let’s assume a CDN has a POP in India, but they reserve it for higher paying clients or chose to serve some or most of the requests from elsewhere, instead of serving it locally.

We as website owners wouldn’t have any way of knowing this with standard tests, so I was wondering if it is possible to check which POP is actually serving the resources so that we can make an informed decision, instead of relying upon the marketing of CDN provider?

You get the IP address in the results. I can’t tell you the physical location because the IP-to-location tools suck at geo-locating CDN POPs. If there is one you are particularly curious about you can do a traceroute to it. The connection latency to the POP will also give you an idea how far away it is.

If your CDN does TCP Anycast then the IP address also won’t tell you much since the same IP address is assigned to all of the POPs and you will have to rely on a traceroute from the test location.

Thanks Patrick