Sucuri Support

Sucuri explains there IP ranges here.

Add Sucuri IPv4 addresses:

nano /vddos/conf.d/cdn-ip.conf

# Sucuri IPv4:
set_real_ip_from 192.88.134.0/23;
set_real_ip_from 185.93.228.0/22;
set_real_ip_from 66.248.200.0/22;

Add Sucuri IPv6 addresses:

nano /vddos/conf.d/cdn-ip.conf

# Sucuri IPv6:
set_real_ip_from 2a02:fe80::/29;

NOTE: But if the server does not have IPv6, vDDoS may not launch
Remember to leave "real_ip_header X-Forwarded-For;" at the end of the file like this article.