I have one client connected with MT CPE that issues IP to client device. MT device is dhcp-server. Client device is D-link wifi router.
I client's laptop directly connects to CPE with Ethernet cable, dhcp data is exchanged and everything is fine.
If client's brand new wifi router is connected to Ethernet cable, it only works some time and than looses IP address and gw and dns setting. (wifi router is dhcp-client). After that, even after reset of the wifi router, no dhcp data is exchanged between MT device and wifi router.
If wifi router is set to ´access point´ mode and thus as bridge it is not passing dhcp request fm laptop to MT device, nor does the wifi router get an IP from CPE.

Changed this brand new wifi router for other brand (TP-Link) and new router and the problem is exactly the same! These routers work normally fine in my network, I have about 60 of these running.

Both troubled routers back home at my desk don't have a single problem to request and or pass dhcp data.

We already replaced all Ethernet connectors several times and basically are out of options.

Any suggestions?


While writing this, I see in the MT log that that the dhcp-server is offering the lease, but it is not successful...

It seems your client does not answer to DHCPOffer message, server is waiting for DHCPrequest but it does not get it (error printed to the log, lease offered without success).

If you are 100% sure about client sending DHCPrequest, we will need to see sniffer output from DHCP server.

Well, first wifi router (=client device, = dhcp-client of MT-CPE which is dhcp-server) home at my desk works as a charm. First time dhcp request followed by lease immediately and after 16 hours still ok.

Second wifi router at client according to server's log shows that the lease is offered from 16:34 until 18:40 to the mac address of the wifi router without success.
Client disconnected router and used laptop directly connected with cable to MT-server. ip requested, offered and accepted at once. Client uses laptop from 18:42 until 20:30. No problems.
After that she followed our advice and hooked the wifi router up again and it requests, and receives IP immediately. Since 20:30:45 last night wifi router is connected and has dhcp received IP running.

Yesterday I did at some time change the MT Ethernet interface setting from auto negotiation into manual and 10Mbps only.
Before I saw the port regularly switching between 10 and 100mbps.
This morning I switched the MT interface back to auto negotiation with 100Mbps selected but wifi router after a reboot just connects to 10Mb again. But it connects and gets an IP!

So maybe the port speed auto negotiation has an error somewhere. Same TPLink wifi routers are connected to several of my other clients with 100Mbps in auto negotiation. A bit weird.