I was recently asked this question as a follow-up to the interview question “what happens when you type cnn.com in the browser?”. The answer to the main question is on a high level, i.e. starting with checking the browser’s cache for the domain name. If it does exist then it uses that, if it’s not found in the cache to checks the router’s routing table… etc.
So when I was asked to drill down a bit further; how is the domain name resolved on the local computer? I responded that it checks the browser’s cache. Wrong!! It turns out that domain lookups are stored in a DNS cache which is a temporary database maintained by the operating system. So this is the first place it looks in order to resolve the domain name.
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