WLC 5508 and WPA/WPA2 causes client DNS lookups to fail

Question

Hi all, we just recently received a brand new 5508 with 6.0.199.4 firmware.  We currently have three LAP-1250s that associate just fine to the WLC.
For testing purposes only, we enabled WPA2 with both types of encryption TKIP and AES with an ASCII PSK.   The clients are able to connect, authenticate and get an IP address from our local (same subnet) DHCP server.  They also get the DNS info from our DHCP server.   However, the problem is that they are not able to do any DNS lookups.   I haven't run wireshark yet to confirm, but it sounds very familiar to this problem: https://supportforums.cisco.com/message/3202369
I've even had clients use nslookup with both of my DNS servers and they are not able to resolve.  I'm not sure if the request or the reply is being blocked/dropped, but I can find out tomorrow.
Now the strange part - if I turn off WLAN security altogether, it works!   That's right, I just disable L2 security for the WLAN and re-connect the clients and they are able to do full DNS lookups.
AND - if I leave L2 security configured (WPA2 with PSK), and enable L3 Passthrough security - the clients get to the auth web page, click the "accept" button and are then able to do full DNS lookups too.
What could be the problem here?   There's nothing I see configured for the L2 or L3 security settings that could be the culprit.  We're using default (from Cisco) configuration, so there's no ACLs configured or anything like that to block DNS.
Another strange thing here which may or not be related - during initial configuration the setup asked for a virtual IP - so I gave it one - 1.1.2.2.   Now when I do an ipconfig /all on the client, I see this 1.1.2.2 address listed as the DHCP server.  Why is this?   It's definitely getting an IP address and DNS info from the correct DHCP server, so not sure why this is showing up.
Thanks, Matt

Answer 1

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Hi Matt,
Just wanted to jump in, and also mention it may be worth attempting to disable the fastpath feature on the 5508, and test your failing client again.  You may be hitting CSCti34667.
debug fastpath cfgtool --fc.disable
This command can be run via Telnet/SSH.  Please keep in mind that fastpath will automatically re-enable periodically, so we recommend disabling every 10 minutes as a workaround for any known fastpath issues.  You can do so by running the following Macro in TeraTerm:
:mainloop
   sendln "debug fastpath cfgtool --fc.disable"
   pause 600
goto mainloop
If you find that disabling fastpath resolves your concern, you can reach out to TAC for an Escalation Image with the fix for this one.
Best,
Drew