Checking Textbox's all rows

Question

Hello,
I want to check a textbox's all rows. For example a user will write some IP's to textbox, and then I will check all of these IP's that if they recorded to db.

Textbox is;
--------------------
12.12.12.1
1.1.1.1
4.5.5.5
4.56.56.56
...
--------------------
Then I have a db that recorded Ip addresses. I want to control that which one of them is recorded before, and which one of them isn't recorded.

How can I check every row's IP's?