What ports need to be open for DNS to work?

What ports need to be open for DNS to work?

The basic firewall rule for allowing DNS queries is to permit inbound UDP and TCP traffic from port 53 to any port from the DNS IP addresses.

Should UDP ports be open?

There is no such thing as an “open” UDP port, at least not in the sense most people are used to think (which is answering something like “OK, I’ve accepted your connection”). UDP is session-less, so “a port” (read: the UDP protocol in the operating system IP stack) will never respond “success” on its own.

How can I tell if a port is open in DNS?

Press the Windows key + R, then type “cmd.exe” and click OK. Enter “telnet + IP address or hostname + port number” (e.g., telnet www.example.com 1723 or telnet 10.17. xxx. xxx 5000) to run the telnet command in Command Prompt and test the TCP port status.

Do UDP ports listen?

As mentioned in the comments, UDP is connectionless. Unlike with TCP, it has no concept of “listening”, “established”, “closed”, or anything like that. If a UDP port is open, it appears in the listing; if it’s not open, it doesn’t. There is no other state to display.

How to check the number of UDP ports in DNS server?

If you use netstat -ano command, it will show all UDP ports mapped to DNS server I noticed it on Windows 2003 DNS servers. You can show the number of UDP ports that DNS us using in this was, with this one-liner: What are the random socket connection issues that customers may experience when installing this security update?

Are there any open ports in dns.exe?

I just examined and found tons of open ports by DNS.EXE. Currports displays UDP local ports from 50000 to 56000, local addresses are :: and remote addresses are empty. Last lines of netstat – a command are below: I didn’t notice these ports before, so I don’t know for sure it is ok or not. What do you think?

How many ports does dns.exe allocate in Windows Server?

After restarting the DNS service, DNS.EXE allocates 5000+ ports. It doesn’t consume extensive memory or cpu. However I noticed/alarmed many http/smtp/pop3 connection problems to the server because of timeouts.

How to avoid DNS fault in Windows Server 2008?

Open an elevated Command Prompt (Run as Administrator…) If you’re on Windows Server 2008 R2 and just want to make sure that a number of individual UDP endpoints are not used by DNS, you can also specify a list of port ranges to be excluded from use by DNS: Thanks for contributing an answer to Server Fault!