view ESXi arp cache

ESXi version 6.5.0

to discover if IPs are in use or not...

ssh to esxi host (if enabled), ping range with script like...

[admin@localhost:~] for i in `seq 254`; do ping 192.168.0.$i -c 1 -W 1 | grep "1 packets received, 0% packet loss" &> /dev/null; if [ "$?" == "0" ]; then echo "192.168.0.$i is USED!!!!"; fi; done
192.168.0.1 is USED!!!!
192.168.0.4 is USED!!!!
...

view arp cache with command...

[admin@@localhost:~] esxcli network ip neighbor list
Neighbor      Mac Address        Vmknic    Expiry  State  Type
------------  -----------------  ------  --------  -----  -------
192.168.0.1  00:12:ef:34:cd:67  vmk0      -4 sec         Unknown
192.168.0.2  (incomplete)       vmk0      -2 sec         Unknown
192.168.0.3  (incomplete)       vmk0      -2 sec         Unknown
192.168.0.4  b4:05:43:03:41:fc  vmk0      -2 sec         Unknown
...