Just a couple days ago, I ran into a problem where my server’s firewall became too aggressive and decided to block my content delivery network’s (CDN) IP address for a particular city.
In this circumstance, the CDN’s Amsterdam location was being blocked. That is a huge problem.
When I loaded the page, even logged out — while logged in, I don’t use the CDN to replace anything or cache anything — I was seeing everything as I expected. That’s because I was hitting MaxCDN’s Los Angeles edge location. (MaxCDN network)
[seealso link="http://go.wpforce.com/maxcdn" title="WPForce uses MaxCDN.com, you should try them out."]
How did I discover that a particular edge server was being blocked? I happened to be running a test on Pingdom.com’s speed test, and I noticed that the Amsterdam testing location was taking more than 60 seconds to load — and every file on my CDN hostname (wpforce.net) was timing out.
Immediately after LiquidWeb finished adding the IP addresses to the white list, service began flowing just as I had expected.
You may or may not run into this problem, depending on how your hosting provider operates it firewall rules. But this is certainly something to be careful of, and if you can ahead of time, make sure you’ve already checked with your CDN provider and hosting provider to ensure there is never a future issue with IP addresses being blocked.