How about splitting your IP addresses up first
Select the column of IP addresses (have three columns empty to the right), from the Ribbon - Data - Data Tools -Text to Columns, follow prompts using "." as a delimiter
Label the four columns A, B, C & D
Select all four columns with headers plus adjacent columns with data to move with the IP addresses
Ribbon - Data - Sort & Filter - Sort and select C for the first sort and D for the second level sort
(I guess you won't need to sort on the first two groups for a private IP address range)
Then in the fifth column use a concatenation to pull them back together
BTW I think that the sort order is based on a character sort algorithm, as the IP addresses will be treated as text.