It is hard to see the information in your screen shot but ACS 5.4 and later support IPv6 for network devices:
Also, if you type an invalid IP address in ACS you would get the following error:
A valid IPv4 address consists of four numbers (0-255) separated by periods, e.g. 184.108.40.206
A valid IPv6 address is n:n:n:n:n:n:n:n where the 'n's are either digits (0-9) or letters (A-F)
I hope this is what you were looking for!
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