When troubleshooting console issues, and in particular iSCSI connectivity problems, you may read the documentation that will suggest that you use both ping and vmkping to test connectivity to your iSCSI target. With ESX this is necessary as the service console will handle discovery and authentication to the iSCSI target (and thus you using ping) and the vmkernel will handle data transfer (and thus you use vmkping).
But with ESXi there is no service console VM and all iSCSI traffic is going through the vmkernel. Thus you only need to use vmkping Why not use ping or ping6? In both cases, they just point to the vmkping binary.
~ # ls /bin/pi* -l
l--------- 0 root root 1984 Jan 1 1970 /bin/ping -> /sbin/vmkping
l--------- 0 root root 1984 Jan 1 1970 /bin/ping6 -> /sbin/vmkping
~ #