WLAN clinet using LAN DHCP

RouterOS General
1

Hello all I have one extremely strange issue.

One (and only one) client on my network is constantly connecting to LAN DHCP server even though its connection over CAPsMAN to WLAN.

All the settings for the CAP are correct, and other clients correctly report @cap1 join to wifi and WLAN dhcp. However one client as mentioned gets straight LAN DHCP.

Here is where it gets stranger. I have another CAP with identical config, and on that one it correctly connects to @cap2 and uses WLAN DHCP.

Also even stranger still i can not remove the LAN ARP of it. If i do it pops straight back, even with the client removed (turned off).

Any ideas? Im kinda lost here.

2

Ok let me simplify the question:

What is the best way to force a client to register to the CAP interface?

3

I’m not sure I understand your setup and the problem, so I’m just guessing what’s going on. If a client can obtain DHCP lease from “wrong” DHCP server, then this indicates that both “right” and “wrong” DHCP server reside on same L2 (switched/bridged) network. And this is not right, you have to investigate and correct the issue. And it isn’t client’s wrong doing, it is network topology.

4

This is what is confusing me here.

Cap is set to “WIFIBridge” (it has its own IP pool) and DHCPserver is set to “WIFIbridge” with the same pool defined.

All clients follow this, and connect to WIFI Dhcp. They also register in CAPsMAN registration table.

But one acts like it is plugged in, and goes straight to LAN DHCP, and also is not seen in CAPsMAN registration table. If checked in bridge Hosts it just acts like its plugged in, stating ethr17 as interface. But it is not its wifi only.

So is there a way to force it to CAP interface?

5

Can you post both router config and CAPAC config?

6

sadly i can not, against company policy. I can only answer specific questions.

7

What you likely see is that the “closest” DHCP server responds faster to initial DHCP discover packet and then device communicates with the one responding first. Perhaps this one and only device (mind, rightfully) decides to talk to some particular DHCP server even though both reply?

The question remains: do really both DHCP servers reside on same L2 network? And, if yes, why do you want it this way? Protocol-wise there can only be one DHCP server on any L2 network (there can be more, but they have to synchronize lease data). All the rest is bad practice leading to various problems.

8

Well the WIFI network has its own Bridge defined, and specified in the CAPS config, so i dont see it as the same L2 network, or do you need to go deeper?
Also out of at least 100 WIFI clients only one has this problem. (the client is a “smart speaker” so no real way to configure it by itself)
All other clients connect with CAPsMAN stating @capX when connecting, and puts them in the registration table.

Also should not CAPsMAN handle wifi clients? Than on basic home setups with only one DHCP server, this kind of problem would be all over the place.

9

Just to add i did notice that the WIFI DHCP has authoritative 2s delay set up. However this does not cause problems to other clients as mentioned.