Does apache log client IPs per request by default? If not, what are some common ways to do this?
Yes, Apache logs the IP addresses that request resources from it. By default, the logs are stored in /var/log/apache2/access.log, but you can check your Apache config file at /etc/apache2/sites-available/your site under the CustomLog directive.
Yes, it does. Please read http://httpd.apache.org/docs/2.2/logs.html#accesslog for more info.
Yes it does by default as much as i know. We dont have to do any special configuration to get client ips in apache's access_log. it comes by default