[Mastrolindo83]

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?

[notagh0st]

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

[Mastrolindo83]

Just tested, same result.

[DramaKing]

Just tested, same result.

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

[zeroday12]

You're most likely getting blocked by a host.

[linkinpork]

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!

[Mastrolindo83]

Remove the -T4 flag does the trick. Thank you