Network monitor

I’ve loged in to one of our routers and whent into the SH IP ACCOUNTING log. I noticed two computers had moltiple sites opend, I called the user and asked how many web pages he had open he said none was not on the internet. How can I find out a web page by the IP address I tried going to the address bar and put the destination IP but page could not be found. Is there a software out there that will help me moniotr my network?
Thx,