All clients stuck in DHCP_REQD

[krock]

HI all,

I have a 5508 WLC controller running 8.3.143.0 software version. This is a new setup I put up so I can steer away from testing in production. I have this controller connected to two Nexus 9k's in a vPC. Every client that trys to connect to my test WLAN gets stuck in DHCP_REQD. I am getting my DHCP from a remote computer and have tested dhcp using wired connection directly from the switch and that works. I have disabled all DHCP options on the controller as well. I get a link local ipv6 address but not ipv4. 

I have attached a debug of me trying to connect my phone to the WLAN. I also tried this on a wide open WLAN with the same result. There is no firewall in-between or any other security device that might block dhcp requests. 

Thank you 

[superego · Accepted solution]

Still same issue on the debug, only up to first step of DHCP process, Discover.

I see your WLC is dual homed to the Nexus switch from the diagram you've provided.  As per Cisco doc, it should be only connected to one switch.  Can you shutdown the ports on switch 2 where the WLC ports are connected?

https://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/8-6/b_Cisco_Wireless_LAN_Controller_Configuration_Best_Practices.html

• For LAG scenarios, using VSS, stacked switch (3750/2960), or Nexus VPC, should work as long as the fragments of an IP packet are sent to the same port. The idea is if you go to multiple switches, the ports must belong to the same L2 “entity” with regard to load balancing decisions.

[krock]

Welll that did the trick.. Thank you... 

Now I have another question in regards to this. We have this exact setup in 4 different Data centers where it's dual homed to the nexus switches and I never seen this issue come up. We do have different Wireless hardware. It's the newer 5520 and 3504 controllers. Do those handle DHCP request differently? 

[ajc]

Did you try VPC instead of just shutting down one of the links going to N9K? Like the picture below where the server would be your WLC?. I am not sure you are facing the basic VPC forwarding rule limitation. How is the DHCP connected to your N9K?

DHCP operation is the same for all the platforms. (I have 5508/8510/8540/2500)

[krock]

I am not understanding your question? Did ou mean if I have tried to limit the links in the vpc membership to the WLC? 

[superego]

Considering the WLCs have the same code, different hardware will not make a WLC act to DHCP differently.

You said that it works on other Data Centers.  Is it possible that you connect this WLC to the one working and test?  Check the NXOS of the Nexus as well.

If you have an HA Pair that you’ll deploy for the WLC you’re testing.  Work around is to do a regular port-channel.