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New Member
Posts: 7
Registered: ‎12-01-2016
Kudos: 1

Clients get old DHCP leases, issue only happens through Unifi APs

[ Edited ]

Our organization has multiple sites with provider-managed routers and switches, some APs use plain access ports (no VLAN tagging), some have VLAN-tagged SSIDs along with a single untagged network as default (which can reach the DHCP server). DHCP leases are given by a Windows Server for our internal network and by the routers for guest access. When using our DHCP server, Cisco's IP-Helper is used to guide it to our DHCP server and it works as intended.

 

We have had multiple cases where clients who were at site X hours or even days ago, get an IP from site X but at site Y. X and Y can be any of our sites, the only constants we have figured out are:

- the IP address leased is coming from the pool it should come from (so 10.0.22.44 is leased from 10.0.22.0/24 DHCP subnet).

- it's not the lease time, these are set at 15 minutes.

- it's only Wireless clients and consist of various Windows 10 laptops and iOS/Android smartphones.

- disabling/enabling the WLAN adapter, rebooting the computer, ipconfig /release and /renew don't help, disconnecting it from Unifi AP, rebooting Unifi AP or blocking it also doesn't fix it. I need to block the IP address that is wrongly leased in the DHCP server and then after a disconnect it will acquire a correct address.

- the issue happens not just with DHCP addresses coming from our Windows Server, but also with ones supplied by a router.

- DHCP guarding isn't enabled and it won't work as we haven't installed Unifi switches yet.

- Controller version 5.9.29 using Unifi AP (classic), AP-AC Lite, AP-AC-Mesh with not latest but recent firmware.

 

The provider claims their switches/routers are configured correctly and it does work correctly over wired LAN even when using devices that have this issue over WLAN.

 

Any clues would help, I'm not experienced enough with Wireshark to wield it but I hope someone has a clue where to look.

Emerging Member
Posts: 140
Registered: ‎04-06-2019
Kudos: 15
Solutions: 4

Re: Clients get old DHCP leases, issue only happens through Unifi APs

On windows, ipconfig /all should list the machines ip info as well as the addy of the dhcp server.
Maybe it ain’t coming from where you think it is.
Senior Member
Posts: 2,815
Registered: ‎04-21-2015
Kudos: 421
Solutions: 112

Re: Clients get old DHCP leases, issue only happens through Unifi APs

[ Edited ]

How is this UniFi issue? Or you just 

seeking for help?

Thanks,
Myky
CWSP
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Don`t blame the device as it`s always doing what you have asked it to do, this is not always the same as what you want.
New Member
Posts: 7
Registered: ‎12-01-2016
Kudos: 1

Re: Clients get old DHCP leases, issue only happens through Unifi APs

I'm not sure it's a Unifi issue but I'm also not sure it isn't. Since this only happens on our wifi network (all Unifi) and my suspicion is this is either a feature that needs an option flipped (that might not be available) or this is an option I need to adjust on the DHCP server.

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Senior Member
Posts: 2,815
Registered: ‎04-21-2015
Kudos: 421
Solutions: 112

Re: Clients get old DHCP leases, issue only happens through Unifi APs

Your task is to confirm the following so that you can rule out an issue with UniFi (or prove that there is an issue with it):
* when the client associates with the SSID, what tag AP is assigning for the traffic (it includes initial DHCP Discovery etc)?
Thanks,
Myky
CWSP
--------------------------------------------------------------------------------------------------------------------------------------------------
Don`t blame the device as it`s always doing what you have asked it to do, this is not always the same as what you want.
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