We have been using Cisco NAC since 2009 in conjunction with our Cisco
Wireless LAN Controllers for Wi-Fi access.  Our NAC is running in the
in-band Layer 3 virtual gateway mode.

We also have been experiencing the NAC Agent pop-up issue starting this
month--which was right after we upgraded from NAC 4.8 to NAC 4.9; during my
tests, some of my laptops will have the NAC Agent pop-up but most of the
time it doesn't.   

I opened a Cisco TAC case three days ago and he had me run Wireshark on my
test laptops to see if the NAC Agent was sending UDP and TCP packets to my
Clean Access Manager (CAS)--the laptops are sending the packets.  After
hours of troubleshooting, I have found out a way to always make the NAC
Agent login pop up--by opening a command prompt and then entering
ipconfig/release and then ipconfig/renew; this was actually a procedure
suggested by my TAC support engineer.  This workaround always works, but it
is a hassle to have  to announce and teach our students to do that procedure
as a workaround.  My TAC support engineer wants us to do some packet
captures from our CAS and Wirless LAN Controller to find out the root cause
of the problem, but we are hesitant to do this.  We are thinking this
problem might be a software bug in NAC 4.9 because it started happening
after we upgraded to 4.9.

Has anyone had this problem with NAC version 4.8 or lower? Or are the only
sites having the NAC Agent pop up problem running 4.9?


 Wayne Lai
 Network Engineer
 University of La Verne
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