Check port availability behind firewall from Linux

In Microsoft Windows, if you want to check, if desire port is reachable on remote system, you use telnet client. How about Linux? How to check port availability behind firewall from Linux? You can use tool called nc (arbitrary TCP and UDP connections and listens) with parameters.

In below example, I checked availability of ports needed by Nutanix DR. I did nc from one Nutanix cluster (CVM) to remote Nutanix cluster (CVM).

nutanix@NTNX-15SM65300246-A-CVM:10.4.91.56:~$ nc -znw1 10.4.91.57 2020
Connection to 10.4.91.57 2020 port [tcp/*] succeeded!
nutanix@NTNX-15SM65300246-A-CVM:10.4.91.56:~$ nc -znw1 10.4.91.57 2009
Connection to 10.4.91.57 2009 port [tcp/*] succeeded!
nutanix@NTNX-15SM65300246-A-CVM:10.4.91.56:~$ nc -znw1 10.4.91.57 22
Connection to 10.4.91.57 22 port [tcp/*] succeeded!
nutanix@NTNX-15SM65300246-A-CVM:10.4.91.56:~$

If you would like to learn more about Nutanix network ports, have a look at my blog post – Nutanix network port diagrams. Where you can find port diagrams for Nutanix in different configurations.

Read nc tool Linux manual to learn more about switches