DNS (Domain Name System) is the internet's directory. A DNS zone for a domain holds records, and each record type answers a different question. Knowing the common types helps you set up websites and email and troubleshoot why mail is rejected or a site will not load. This lesson also covers two network concepts the A+ exam groups nearby: VLANs, which separate traffic inside a network, and VPNs, which protect traffic crossing an untrusted network.
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