Problem: Clients Not Getting DHCP

Hi all,

Pre-face: I am not a networking expert. I'm a sysadmin with a solid grounding in the essentials.

Description: I have a remote site which will not get their DHCP addresses in a timely fashion. It can take up to 30 minutes for the client machine to pull an address. I have a total of 30 remote sites, and this is the only location that I have this problem at. Additionally, it is only a portion of the building that has this problem. The building houses about 160 people and a similar number of devices. The problem is intermittent, but occurs most frequently after a user has transported their laptop to a different network. Problem persists after reboot. I have successfully replicated on my own laptop. I have 508 leases available for DHCP, and exceeding the available pool is not the issue.

Infrastructure involved: Windows server 2012R2 domain with an onsite RODC. Sonicwall TZ400 router, Three Netgear GS752P switches in single ring topology, Unifi AP-AC-Pro WAPs. Clients are a mix of different HP laptops with differing wireless NICs. (FYI, switches are being replaced with M4300 units in a 10G collapsed core RSPT setup. This is part of a planned upgrade and not a troubleshooting step for this problem.)

Steps I have taken: Bypassed the RODC and distributed DHCP through the router, sending the clients to central office for DNS/AD. Replaced the switch serving that area with known good hardware. Replaced the router with known good hardware. Replaced the WAPs (2) serving the area. Rebuilt the wireless network. Hard wiring the computers solves the problem, but there are very few ports available for doing so and as a practical matter is not acceptable for daily operations.

This seems to indicate a wireless problem, but after replacing the WAPs and reconfiguring the wifi, I have a hard time accepting that. The only thing I can think of is that the actual cables / patch panels serving the WAPs are the issue. But, thats why I'm asking for help! What do I not know that I don't know?

Thanks for your help!