При попытке пинга несуществующего хоста командой 
ping -c n xxx.xxx.xxx.xxx
не завершает свою работу, а ждет непонятно чего,
Control-C например.

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 [<a href="mailto:user@user" target="_new">user@user</a> user]$ ping -c 3 192.168.100.250
PING 192.168.100.250 (192.168.100.250) from 192.168.1.4 : 56(84) bytes of data.
WARNING: kernel is not very fresh, upgrade is recommended.
From 192.168.1.4: icmp_seq=1 Destination Host Unreachable
From 192.168.1.4 icmp_seq=1 Destination Host Unreachable
From 192.168.1.4 icmp_seq=2 Destination Host Unreachable
From 192.168.1.4 icmp_seq=3 Destination Host Unreachable

Давим Control-C:
--- 192.168.1.250 ping statistics ---
3 packets transmitted, 0 received, +4 errors, 100% loss, time 1999ms
, pipe 3