We have an office with 9 users, a network printer and a NAS box. They are all connected to a HP switch which is connected to a Watchguard Firebox 10E router.
A couple of weeks ago a user called to say he had been working at another office that morning and when he returned and docked his laptop his couldn't connect to internet. He was receiving an IP from the firebox but he couldn't access anything external. The fix was to reboot the watchguard. He then has access straight away.
This happened again yesterday with another user who took his laptop home to work on in the evening. When he came in to the office, same problem. We rebooted the watchguard - fixed.
It has happened again today - another user who left the office with his laptop came back in and we had to reboot the firebox.
Initially I thought it was watchguard license issue - we have 15 licenses, but we have around 12 devices using the watchguard so it can't be that.
They do get an address from the watchguard - they just can't access anything external.