DHCP Client Getting Unrecognised IP from Wifi AP

I am seeking some guidance here as I do not understand what is going on. I have a firewall router with three ports set up with each port on a different subnet and with DHCP enabled. On two subnets there are Wifi access points as well as wired connections and wifi clients using DHCP are served addresses from the firewall router through the APs. This usually works OK but recently I have found that clients are connecting to the APs but are then given an unrecognised address which is not within any of the subnets I use and not, in particular, from the address pool available from the DHCP server for the subnet in question. In consequence the client cannot access the wan because it is on a different subnet from the gateway. The problem is intermittent and cure seems to be rebooting each device in turn (just like windoze!)
It is almost as though the request for an address is being passed through the firewall router and a DHCP server on the Wan side is issuing an address.
I am not sure if this is even possible but am out of my depth here and would appreciate some help on how to diagnose what might be happening.

Too little information.

What version of opensuse are you running?

What desktop are you using?

Are you using “NetworkManager” or “ifup” settings or “wicked” (new for 13.2)?

What IP address are you getting? In particular, does it begin with “169.” which is an avahi assigned address when DHCP is not working properly?

Maybe, for good measure, what network card are you using?

Hi and please forgive the absence of data. I am having difficulty reproducing the problem and have an issue with my routers which I must sort out first. Will get back to you.
Thanks again.

You have to track down where is the origin of the mysterious IP addresses.
I trust that your “firewall server” is not requested by the Clients to provide an IP address.
This can be derived from /var/log/messages and should look like the following if an IP address is provided:

2014-11-14T17:33:28.187193+01:00 fhserver dhcpd: DHCPREQUEST for from 00:22:4d:af:f6:1a via eth1
2014-11-14T17:33:28.187614+01:00 fhserver dhcpd: DHCPACK on to 00:22:4d:af:f6:1a via eth1
2014-11-14T17:37:47.267899+01:00 fhserver dhcpd: DHCPINFORM from via eth1
2014-11-14T17:37:47.268349+01:00 fhserver dhcpd: DHCPACK to (00:22:4d:aa:93:6c) via eth1

Otherwise it is someone else to provide the murky IPs.

I suspect it could be your AP routers which might have some DHCP Server running. What are you using there?

I have overseen that you have some Window$ clients.
Check if one or more of your clients are providing WLAN access (tethering) to others.
They could be the Problem.

Hi, yes we have many clients, windoze, android, iphones etc but how did you know?

I am not responsible for these and have no idea if tethering has been set up.

The unknown IP was Not sure if this comes from avahi or is a windoze system fall back.

I now find one of my broadband connections has been down a couple of days so on limited bandwidth at present. Will do some more work and get back.