clients on flexconnect AP unable to get dhcp address after wlc upgrade

[Julio Coral Orbes]

Hi support community,

I have a WLC 2504, with 30 APs 1130 in flexconnect mode. The WLC runs code version 7.0.240.0. In order to register new ap models, we need upgrade to a recent code.

In the last upgrade attempt, to version 7.4.121.0, all the AP joined the WLC, the vlan mappings in flexconnect were checked and were fine. However the clients were unable to get a DHCP address (169.254.x.x). The DHCP server is local for each location, usually is a 3750x that acts as core switch.

connecting via cable, clients got dhcp address. so dhcp server isn't the problem. Upgraded to code 7.6.100.0, but got the same behavior.

Finally we decided to downgrade the wlc to code 7.0.240.0 again, and everything started working again, however i need upgrade as we are buying the new access points models.

Someone else has had a similiar issue?

thanks

[Scott Fella]

I upgraded a school district from v7.0.240.0 to v7.4.121.0 with FUS 1.9.0.0 and no issues with FlexConnect.  Maybe upgrade teh FUS if you haven't yet.

http://www.cisco.com/c/en/us/td/docs/wireless/controller/release/notes/fus_rn_OL-31390-01.pdf

Thanks,

Scott

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[Julio Coral Orbes]

Hi guys,

in the next upgrade attemp, i definetly will upgrade the FUS also.

The native vlan on the trunks is the vlan 3, however i think we can also try changing to a high value as the bug workaround suggested..

EDIT: Upgraded the FUS to 1.8.0.0 and the software to 7.4.121.0 but the behavior was the same. Got an engineer special code version 7.4.121.9 from the tac and the issue was solved. The bug is not unique for native vlan 2, in my case the native is 3. As i undersand it affects when you have vlans greater than the native vlan on the flexconnect mappings.

thanks,

[Rasika Nayanajith · Accepted solution]

Hi,

What is the native vlan you are using ? If it is vlan number 2, then there is known bug CSCui73764

Symptom:

Flex mode APs 1130 & 1240 series, will not pass traffic, e.g. DHCP, ARP. on some wlans.

Conditions:
1) Flex connect local switching
2) AP 1240 or 1130
3) any version before 7.4.121.7
4) native vlan x, non working vlan y.
5) user unable to get ip address.

Workaround:
change the native vlan to an unexpectedly high number, so no wlan will ever get mapped to a bridge group number that high.

Further Problem Description:
telnet to the flex ap. here is an example. vlan 3 is the native vlan on the flex ap, it is correctly mapped to bridge group 1. now the wlan which will not work is the one, which is mapped to vlan2. see carefully below, the vlan 2 is mapped to bridge group 3. this is the instance where we hit the bug. so it can be any wlan-vlan-native vlan combination. 

HTH

Rasika

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