Internet is playing a more and more important role in today's society. Wireless network and mobile devices are becoming part of our lives. So it's significant to learn about information of the users or network usage for both network researchers and managers of fixed/wireless network. Previous methods of user characterizing and network usage are mostly based on TCP traffic study. But when facing to a large amount of users, raw packet capturing and storing would be difficult. Also, there were previous methods researched the fixed network or wireless network, but a comparative study is hardly seen. So in this paper, we measured the large-scale fixed and wireless network of our campus via DHCP analysis. We analyzed the user behavior such as distribution of user online time, user count and join/leave time-stamps. We also studied about users' operating systems by introducing DHCP OS fingerprinting. We found some interesting results, which revealed the trend of mobile network and some challenges might be brought in.