Find CDNs used by a website
There is a way to load balance CDNs to make sure that our users to go the right, read best performing CDN. To learn more about this, go through my talk here: SRECon EMEA 2017. Video at: Youtube Link
I wrote a tool some time back which can be used to identify the various CDNs used by a website.
Find more details here: GITHUB Link to the project
The way it works is, it tries to resolve the FQDN from various location around the world in a hope that the FQDN resolves to different CDN owned CNAMEs. Then, this tool maintains a list of CNAMES -> CDN Name mapping. This data is represented nicely in a table.
Same output from the tool to help you understand what I'm talking about:-
➜ $?=0 shadyabhi/cdnfinder [ 4:48PM] (master|…) % ./cdnfinder -domain=static.licdn.com -timeout=0.1s -number-ns=5 -filter-countries=IN,SG,JP
WARN[0000] Skipping a line while parsing csv at line: 46346, column: 0
|-----------|----------------------|-----------------------------------------|----------------|-------------|
| COUNTRY | CITY | CDN/HOSTNAME | IP | TIME |
|-----------|----------------------|-----------------------------------------|----------------|-------------|
| Singapore | SG - Singapore | EdgeCast - cs627.wac.epsiloncdn.net. | 202.136.162.11 | 44.04332ms |
| India | IN - Mumbai | EdgeCast - cs627.wac.epsiloncdn.net. | 203.115.71.66 | 20.700975ms |
| India | IN - Bhubaneswar | EdgeCast - cs627.wac.epsiloncdn.net. | 202.62.224.2 | 61.284302ms |
| India | IN - Mumbai | EdgeCast - cs627.wac.epsiloncdn.net. | 202.138.120.4 | 27.423725ms |
| Singapore | SG - | Akamai - e9706.dscg.akamaiedge.net. | 121.52.206.130 | 44.463913ms |
|-----------|----------------------|-----------------------------------------|----------------|-------------|
INFO[0000] Took 669.099039ms to query DNS servers...
>>> 0s elasped...
➜ $?=0 shadyabhi/cdnfinder [ 4:49PM] (master|…) %