Tnsping doesn't make sense.

Today I'm going to do a few Oracle experiments and suddenly discover Oracle that can't connect to the virtual machine, and dynamic listening won't start.

Issue 1: Dynamic listening does not start

Reason:/etc/hosts in the configuration error, the IP address in the wrong match

Problem 2:listener start normally, but Tnsping doesn't work

Reason:

Client (Windows) using Tnsping server IP to see if it can spell, spell out the server side of the problem, there are two situations:
1, check whether the listener is starting (Lsnrctl status)
2, Fire is open 1521 ports if not open, then edit the/etc/sysconfig/iptables file, add the following sentence
-A rh-firewall-1-input-m state--state new-m tcp-p TCP--dport 1521-j ACCEPT