Netmask is another simple tool which does one thing and that is, makes a ICMP netmask request. By determining the netmasks of various computers on a network, you can better map your subnet structure and infer trust relationships.
If you are using Google Analytics for web analytics it can be beneficial to exclude certain addresses to provide a more accurate view of traffic to the site. There are numerous reasons that excluding IP’s from the analytics statistics such as if it is a personal site that doesn’t do a lot of traffic and you are working on all the time from home the analytics results might not provide a real world view of what other visitors view the most. Another example might be if it’s a corporate web site that numerous developers, QA personal, and others employees are visiting from the same address space it could skew the analytics results because of such a high concentration of traffic from one IP address or subnet. One of the great reasons for reviewing the web analytics data provided by Google Analytics is to see what pages customers view or what region your customers are from. This type of data can help prioritize the areas of the site that should be worked on the most or what content provides the best return on investment and if the data includes your own traffic it might not provide accurate data for you to review.