TestOut LabSim A+ Certification Practice Exam

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Which port must be opened in a server's firewall to allow clients to access the DNS service you have just installed?

80
53
8080
443

The correct answer is: 53

To facilitate client access to a DNS service, the appropriate port to open in the server's firewall is port 53. This port is designated for DNS (Domain Name System) traffic, which uses both UDP and TCP protocols. Clients rely on this service to resolve domain names into IP addresses and vice versa, which is pivotal for locating resources on a network or the Internet. When a client wants to access a website or a service, it sends a DNS query to a DNS server, typically over UDP on port 53. If the query is complex or requires a larger response, TCP can be utilized, but it will still use the same port. By ensuring that port 53 is open, the server can respond to DNS queries, allowing clients to successfully connect to domain names. This connectivity is essential in network communication, as without it, clients would be unable to resolve domain names, leading to failed connections to websites or services.