The notation format for an address is different with CIDR. What we know as the subnet mask is noted in number of network bits appended to the IPv4 address.
Old notation: 192.168.0.0 mask 255.255.255.0
In CIDR notation: 192.168.0.0/24
You can find detailed information in RFC 1518 and 1519. The address specification of IPv6 is different from the IPv4 specification. An IPv6 address has a prefix, which is usually composed of a provider-allocated public prefix, a 16-bit subnet prefix for internal subnets and a 64 bit interface identifier. The prefix length is appended with a slash, specifying the number of prefix bits. It looks just like CIDR.
Check RFC 3513 for the IPv6 address specification.
This was first published in March 2005