TCP port 21 — FTP (File Transfer Protocol) TCP port 22 — SSH (Secure Shell) TCP port 23 — Telnet. TCP port 25 — SMTP (Simple Mail Transfer Protocol) TCP and UDP port 53 — DNS (Domain Name System)

I'd a scan task and I faced following result . Host is up (0.032s latency). Scanned at 2012-10-25 16:06:38 AST for 856s PORT STATE SERVICE VERSION 1/tcp open tcpwrapped 3/tcp open tcpwrapped 4/tcp open tcpwrapped . . 19/tcp open tcpwrapped 20/tcp open tcpwrapped 21/tcp open tcpwrapped 22/tcp open tcpwrapped 23/tcp open tcpwrapped . . 64623/tcp open tcpwrapped 64680/tcp open tcpwrapped … Solved: How to close port 53 - Cisco Community Hello, I have had some customer who experienced this issue. The most likely cause is that one of the PC's on your network, not the router, is infected with a virus and it is generating this traffic, now, since the ISP is not able to see inside of your network, they are pointing to the gateway to … Securing risky network ports | CSO Online TCP/UDP port 53 for DNS offers an exit strategy. Once criminal hackers inside the network have their prize, all they need to do to get it out the door is use readily available software that turns

In the preceding example, there are multiple flows for DNS packets on UDP port 53 (hex value 0035). In this example, the IP address originally sent a DNS query message (request) to the DNS server at IP address using UDP destination port 53 (hex value 0x0035) and UDP source port 1027 (hex value 0403).

Understanding TCP/UDP Port Functions | Network+ Exam Cram The HTTP service uses port 80, so blocking port 80 prevents users from using the HTTP service. Answer A is incorrect because DNS uses port 53. Answer B is incorrect because POP3 uses port 110. Answer C is incorrect because FTP uses port 21. B. The most commonly used port for FTP in modern implementations is 21. < ICMP port number? — TechExams Community

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Port 53 is open for DNS. Why would I need this? You need to have UDP 53 allowed for responses to DNS queries that your server sends, as UDP is a stateless protocol. Don't block it if you want any kind of outbound connectivity, software updates, etc.