If there is a firewall, only PING is allowed, because PING and TELNET are aimed at different ports, and TELNET is blocked. Do not start the other party's related services first, and then have firewall shielding. Telnet can connect, which means that a connection channel has been established between two computers. Theoretically, you can ping. If you can't ping, the possible reason is that the other host turned off ping echo, or the other firewall blocked the packets sent by ping.

Extended answer: Because the failed computer was exchanged after restarting, this result does not conform to the principle of replacement method. Therefore, it is judged as a specific accidental perception or superficial phenomenon, not a real phenomenon; Filter known conditions and PING if telnet is not available. At the same time, the number of CONs that can log in remotely can be adjusted. For example, the default number of general switches is. Telnet release can also be set, so the initial judgment is that the X end is limited.