Solution of wireless link "PCI unknown" on Centos 7.1

After Centos 7.1 tobe installed on my t400, my wireless link "Intel 5100 AGN" cannot be managed by NetworkManager, which show in "PCI unknown" state.

Googled many pages, most of them introduced how to scan wifi links by command line tool "iw", i tried all steps supplied by the pages but was blocked at the last step to get dynamical ipaddress by dhclient command "sudo dhclient wlp3s0 -v". The dhclient always complain "NO DHCPOFFERS received." (I doubted there should be some tricky to play with dhclient but which i am not faimiar with.. sad.. )

But i think there would be some extending tool for NetworkManager to manager wifi, then i google "NetworkManager wifi", i got "NetwrokManager-wifi plugin" from link https://www.centos.org/forums/viewtopic.php?f=47&t=52810

After following steps , i finally make wifi work well on centos 7.1

• yum install NetworkManager-wifi
• reboot machine (i tried logout and login, not work) 

Problem is NetworkManager-wifi is not installed by default on centos 7.1, (would it be my mistake when install OS? strange..)