One for the Excel experts

[Spacecadet]

That won't work unless the only difference between the IP adresses is in the 4th part. If that's the case then it's good enough, but you might need to sort on more than 10 digits.

Edit: looks it won't work at all

If you only need to sort those addresses once, then the cvs file solution is probably the easiest. But if you want to make it automatic, you will most likely have to write some VBA code.

it would work if each of the parts was padded to 3 digits. eg:
192.168.0.1 becomes 192.168.000.001 becomes 192168000001

easily done with:
=RIGHT("000" & LEFT(A1,SEARCH(".", A1)-1), 3) & RIGHT("000" & MID(A1, SEARCH(".", A1)+1, SEARCH(".", A1, SEARCH(".", A1)+1)- SEARCH(".", A1)-1), 3)&RIGHT("000" & MID(A1, SEARCH(".", A1, SEARCH(".", A1)+1)+1, SEARCH(".", A1, SEARCH(".", A1, SEARCH(".", A1)+1)+1) - SEARCH(".", A1, SEARCH(".", A1)+1)-1), 3) & RIGHT("000" & MID(A1, SEARCH(".", A1, SEARCH(".", A1, SEARCH(".", A1)+1)+1)+1,3), 3)