Cannot Obtain IP/Lease without Reboot

[AlexGill]

I'm hoping someone has seen this DHCP issue.

A user at location Walnut acquires an IP from an MX250 no problem, but when visiting location HS (also with a MX250), they can authenticate/associate, but no IP unless they reboot... A packet reveals the visiting laptop at HS is requesting an IP from the Walnut gateway, which fails because the Walnut IP doesn't exist at HS. 

Of note (1) normal users of HS who do not visit Walnut have no problems, and (2) while Walnut uses a full Meraki setup, HS uses a WLC to manage the APs.

[PhilipDAth]

If they plug into HS using an Ethernet cable does it work?

What I'm asking here is - does the issue only happen on WiFi?

[AlexGill]

Hey Philip, missed this -- yes, using ethernet on a problem laptop worked just fine and the time of issue.

So I have been doing work on this and narrowed it down.

Laptops cannot connected because instead of obtaining a new address via a DHCP DISCOVER process, it keeps trying to revalidate -- ithe old (Walnut) IP, likely sensing it's connected to the old network, which is true -- because of our VPN mesh, the old gateway is reachable, and the laptop does not give up it's non-working IP without a reboot.

Currently, I'm focusing on Apple's use of Simple DNA: https://datatracker.ietf.org/doc/html/rfc6059