Ping may fail even if the system is in network

Generally we use PING IP command to test the connectivity of a system.
If it fails we think it's not reachable But it's not true always.
I faced the same situation today..
There is a system for which I can do ssh -p 2021 root@XXXXXX

But for the same box I can't ping.
Learning is ping uses icmp 'echo-request' . If it is blocked in that server we can't ping...