DHCP problems with Homeplugs

[fozzie bear]

I have an ongoing problem with an installation using Devolo dLan 200 AV Homplugs.
These are installed in a large period building of three floors which incorporates new and older wiring. The whole house is supplied by a three phase supply and there is a distribution board on the ground floor and another on the first floor.
The adsl router is located on the ground floor in a newer part of the house. I have used a dlan200 AVMini to inject the signal from the router into the nearest 13amp socket(all adapters are directly in wall sockets). Each bedroom on the first floor and the office on the 2nd floor has a dLan AV 200 Wireless N adapter. Some parts of the house get a reasonable network speed (shown orange in the Devolo Cockpit and indicator leds on the units) but others have a red light up showing network spreeds of 10Mb or less. This varies during the time of day and load placed on the "Network" by laptops downloading/browsing the net.
The main problem I have is getting a connection. If I use DHCP on the wireless adapter of the homplug the client may eventually get a connection but will often time out and self assign an APIPA address. If hower I use a static address it connects OK. I need to use DHCP as the users are mainly laptop users who connect to different networks.
On one fairly static laptop I have connected to the dLan adapter using ethernet and a static IP while at home, leaving the wireless adapter set to DHCP.

I have upgraded the router firmware, changed the router and updated the firmware in the dLan adapters but the problem persists. I have even considered attaching an old router as a second DHCP server in the part of the house where problems persist but I am not sure this would resolve the issue.

Currently each adapter is set to receive an IP address dynamically from the router. I know there is a setting to assign a static address to each adapter. What I am not sure, is if there is an inbuilt DHCP server in these Devolo adapters as there is in some other makes?

If I assign a static IP address to each dLan adapter will the network still pass DHCP traffic to the attached clients?

Any suggestions recommendation gratefully accepted as I am tearing my hair out with this one.

Fozzie

[stevech]

Homeplug and MoCA are "layer 2" devices. An ethernet switch is (excluding $$$$ ones) are layer 2.

Layer 2 isn't aware of TCP/IP let along DHCP which is a use case of IP.

So the error might occur with straight cat5 to the router LAN port.
Or it could be intermittent (try many times before concluding).
If it seems to be HomePlug dependent, than assuming the Homeplug devices aren't faulty, and assuming the signal strength is OK, and no interference, then I'd blame the router as not doing DHCP correctly for all timing cases, or the DLAN device not doing DHCP correctly, or both This is classic.

The DLAN IP address is just for administering it.. that IP address isn't relevant to packets going to/from the two mediums.