Home network with two routers and just one Wifi

Question

I know it is a pretty lame question, but I am not a pro in networking, so I will still ask it. And I will try to explain details where possible.

I want to create the following setup:

Phone line is in the hallway downstairs. I connect unit A to the phone line. Unit A is a combined ADSL modem + WiFi router + 4-port ethernet switch. (correct me if I am not using the terms correctly). The model is D-Link 3680.

Note: I know the modem functions correctly and connects to the Internet (I have tested it). I also know that DHCP in the router functions correctly and I can connect to the internet with my laptop.

I disable WiFi in unit A and run cable (in fact a PowerLine link) upstairs to the third floor.

Note: I have checked that I can connect to the internet on the the other side of the link. I still get address from DHCP of my router and everything is fine

What I want to do now, is instead of connecting to the cable on the third floor, hook up another router that I have. Unit B: Huawei HG533: a combined ADSL modem + WiFi router + 4-port ethernet switch with USB port for Storage Devices. I want to have wifi enabled on it and I want to connect to the internet through it. Obviously I disable modem functionality in this device and just connect the ethernet cable to the uplink.

The problem is, that I cannot connect to the internet once connected to the Unit B. And I cannot ping unit A.

So, could anyone sketch a correct network topology for this setup? What settings do I have to look at? Where do I even start. Which one of two units (or both) need(s) to run DHCP server? Do they have to be on the same subnet? How do I setup default gateways.

   [Internet]
       |
  [Phone Line]
       |
       |
|--------------|                 |---------------|                                        
|   Unit A     |                 |   Unit B      |          |---------------|
|  ADSL modem  |---[powerline]---| ADSL disabled |--[WiFi]--|   Laptop(s)   |
|              |                 |       DHCP?   |          |---------------|
|--------------|                 |---------------|
                                         |
                                         |
                                       [USB]
                                         |
                                 |---------------|
                                 |      HDD      |
                                 |---------------|

Oh, and if anyone is interested in why am i doing it. It is simple: Reason 1: I don't want to have my WiFi Router downstairs because signal is weak on the third floor. Reason 2: I use USB port and connect my 1Tb hdd to it and I don't want to leave it in the hallway, because I live in the flatshare with people I don't really know. Reason 3: I want to have WiFi within my room, not just an ethernet cable.

Sorry for being such a n00b, any advice will be appreciated. Oh, and I have read this thread, but does not provide enough explanation.

UPDATE: in response to CharlieRB's comment, here is a picture of the Unit B:

Answer 1

Ok, so I am finally answering my own question here. The answer is derived from the comments by Max Ried and James Womack. I wouldn't have figured it out on my own. In fact, my original setup was 100% correct. The problem was that Unit B (Huawei HG533) has a bug that does not allow clients connected to it to use external DHCP server. The only change I made was setting static IPs and now everything works.

So what I did was:

• I set address of Unit A (D-Link modem + router) to 192.168.1.2 and connected it to the phoneline.

• I have connected powerline adapter to one of the LAN ports of Unit A and plugged it into the mains

• On the top floor of the apartment I have plugged another powerline adapter into the mains and connected it to one of the LAN ports of Unit B. I have figured out that it does not make any difference if I connect it to one of LAN ports or to the one labeled as "Fiber" - result is the same

• I have disabled WiFi in unit A and enabled WiFi in unit B

• I now connect to unit B and I have access to NAS, connected to unit B and to the internet available through Unit A.

However: I did not manage to setup DHCP. This seems to be the problem that initially did not allow me to create desired setup. I am currently using static IP address for both Unit A, Unit B and all clients connected to Unit B.

There is a setting called "DHCP transparent transparrent transmission" and another one called "DHCP relay" - both have no effect. I have tried enabling DHCP for Unit A and dissabling it for Unit B and putting it into Bridge mode with Transparent DHCP transmission no effect.

Quick search on the internet showed that this is a feature of Huawei HG533 and it seems like no one can get it to transmit DHCP transparently from LAN.

[Link 1]

[Link 2]

Anyway, I am happy with my current setup even though it is static IP. I am planning to replace unit B (Huawei HG533) with Asus RT-N16 running openWrt soon anyway.

Thanks to everyone who helped me to sort this out.

UPDATE: here are screenshots from the interface of Unit B (Huawei)