IP address block in CIDR format, such as 10.0.0.0/24. This is often the address block of the DNS server used for your self-managed domain. For a single IP address, use a CIDR address block with /32. For example, 10.0.0.0/32.
IPv6 address block in CIDR format, such as 2001:db8::/32. This is often the address block of the DNS server used for your self-managed domain. For a single IPv6 address, use a CIDR address block with /128. For example, 2001:db8::1/128.