I'm looking for suggestions on how to design a table to save user's IP addresses. I will be saving the last 20-50 IP addresses used. I will not be storing duplicates (unless that is the most efficient way to go here), but I want to record how many times each IP address was used. (So if I check to see if an IP address already exists, and I see that it does, I might want to somehow indicate the number of times I have tried to update the database with this IP address for this user).

I will use a php script to insert the ip addresses and to check and see if I am inserting a duplicate one, but I am concerned about table design here and how I should store the data efficiently. Here are some concerns:
Currently I have a table with three columns. Column 1 for the id of a user, Column 2 for a single ip, and Column 3 for the date it was used. Each time a user logs in I check to see if that user's current IP already exists as associated with the user in this table. But I am not sure how to expand the table further (and store the data efficiently) how many times a user has used a certain IP.

I am probably overlooking something basic here. Any thoughts?

At the end of the day I want a php script that displays data like this:

//
User Name
1. IP Address 1 (used X many times) (last used)
2. IP Address 2 (used X many times)
//