How to block temporarily comments from specific IP address? Can we block specific IP address for a period of time and block posting comments from that IP address for this period of time? 
Only posting comments, not viewing pages.
I have not used this module but you can check Comment IP module.


  This module displays a comments IP address in the comment overview
  page and allows you the option to "Delete the selected comments and
  block their IP's" from the comment overview dropdown list.