Error: No route to host while ICMP is working

Symptom:

   We try to access a port 1521 service in a VM which has Oracle Linux 7.6 . Ping (ICMP) is working fine. But we get error when we test port via nc or telnet
Ncat: No route to host.

Solution:

  There are quite a few reasons for that.

• check your subnet security list, make sure ports are open
• use traceroute and dig to check route table is working as expected
• check target VM linux firewalld is up 

In our case, firewalld is up by default, it blocks traffic of  1521. The error message is confusing people "Ncat: No route to host." . It is not about route. It is due to traffic blocked by target host Linux

Fix it via systemctl stop firewalld ;systemctl disable firewalld