The link posted by Jon is very interesting and does have what seem to be definitive statements from Cisco employees on both sides of the question. I wonder if the person who confidently says that he has accomplished nat on 3850 says this on the basis of finding a version which accepts the commands, or did he actually test it and verify that nat is working?
It seems to me that the best way to find out is to try it on your switch. In global config or in interface config (for a vlan interface or routed port) do "show ip ?" and see if ip nat shows up as an alternative (or perhaps show ip n? which would produce shorter output). And if the commands show up as available then you need to configure and test to see if nat actually works (because it seems pretty obvious that some versions do accept the command but do not actually work). And that only proves the point for the version that you are running and leaves open the possibility that some other version might support it.
In general Catalyst switches do not support nat. There are some exceptions but I am not optimistic that 3850 is one of them.
HTH
Rick
HTH
Rick
