Hi,
you can disable the ipv6 fro the command line
1.ssh to host on which you want to disable the ipv6
2. Use this command to disable the IPv6 esxcli system module parameters set -m tcpip4 -p ipv6=0
3. Reboot the host
Please let me know if it helps you 
you can also disable using this command:- esxcli network ip set --ipv6-enabled=false
it also needs a reboot to the ESXi host.
Thank you