DHCP failure, no response from DHCP server

[光热斗]

Hi Everyone,

Kinda new to this community, I want to share and ask for help to solve a very strange case in our office.

In our three-story building, 2nd floor works fine, however 3 out of 11 MR 56s on the first floor report DHCP failures, same as our third floor, 3 out of 9 MR 56s do not work as expected. The APs cannot to Aruba switch on a trunked port in the default vlan allows vlan 31 and vlan 100(management). APs' ip address is on management vlan network. 

We have three SSIDs:

1. SSID Private requires 802.11x authentication and uses vlan tagging. 
2. SSID Public uses meraki dhcp 
3. SSID GP uses Pre-shared key, local LAN but no vlan tagging (untagged).

After some troubleshooting here are our findings:

1. PC1 fails to connect to Private SSID with nearby AP24, while PC2 and PC3 can connect AP24.
   1. Shows connecting.....
2. PC1 can connect to Private SSID from AP 26 and roam to AP24 without disconnecting. 
3. PC1 can connect GP and Public SSID from AP 24.
4. After PC1 releases ip address and then fails in connecting to Private SSID from AP24. However, it works for PC2 and PC3 when we do the same test.
5. 4. We check the cable, which it is good. We relocate AP24 to AP26's location and directly connect to Switch. This works for PC2 and PC3 but same issue for PC1.

We use 802.11aw and WPA2 only. When checking the dashboard and pcap file, dhcp fails as no response from dhcp server.

We have two windows dhcp servers for wireless client. If we use switch as dhcp server, would that be a better choice?  

[Ryan_Miles]

I'd recommend engaging Meraki Support. It's impossible to know what's happening without direct visibility to your Org for deeper troubleshooting. DHCP failures could be misconfigured switch ports, DHCP server issues, something else.

[RaphaelL]

What firmware versions ?

On some older version there was false DHCP failures. Those were fixed in MR29.X . That might be the case.

[PhilipDAth]

Are you 100% sure the switch port configurations for all of the APs are the same?  Are you sure that the VLANs being used are presented too all of the switches being used by the APs?

For the APs that fail - do they fail 100% of the time, or is it intermittent?

Do the Aruba switches have any kind of DHCP security function that is enabled?