nmap don't find open ports - Printable Version

nmap don't find open ports - Printable Version

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nmap don't find open ports - Mastrolindo83 - Mar 9, 2024

Hi all

I've been using nmap for a while now. However, it often happens that open ports cannot be found. Here's an example:

Port 5172 TCP is open, synology login page.

Now I'm trying the following scan:

Code 
nmap -T4 -A -O -sV -sC -p 5000-6000 IP

no ports found.

If I use:

Code 
nmap -T4 -A -O -sV -sC -p 5172 IP

will detect it as an open TCP port.

This is just an example and occurs on so many ports. I would therefore have to know exactly which port is open or scan each one individually. 😵

Am I using the wrong command?

RE: nmap don't find open ports - notagh0st - Mar 9, 2024

It could be blocking the pings. Have you tried adding the -Pn flag?

RE: nmap don't find open ports - Mastrolindo83 - Mar 9, 2024

Just tested, same result.

RE: nmap don't find open ports - DramaKing - Mar 9, 2024

(Mar 9, 2024 04:39 AM)Mastrolindo83 Wrote: Just tested, same result.

You're scanning too fast for the network and getting unreliable results.

RE: nmap don't find open ports - zeroday12 - Mar 9, 2024

You're most likely getting blocked by a host.

RE: nmap don't find open ports - linkinpork - Mar 9, 2024

(Mar 9, 2024 04:01 AM)Mastrolindo83 Wrote: Am I using the wrong command?

Hi,

The -T4 flag might be asking for commands too fast. Try either removing it or explicitly stating -T3.

Personally if I have all day I would pull it all the way down to T1.

Cheers!

RE: nmap don't find open ports - Mastrolindo83 - Mar 10, 2024

Remove the -T4 flag does the trick. Thank you