How to correctly describe a small network running multiple DHCP

Question

I have a home network with multiple devices connected to a central router. I have limited ability to change the core of this network (ie mess with the router, put additional cabling in - joys of shared accommodation...) so I have everything running through a homeplug into a room, then it hits a TP-Link TL-WR841N flashed to a recent DD-WRT build which is just a switch with DHCP turned off.

Current setup looks a bit like this:

                                                |                                  |---------------|
|----------|                                    |                               |--|other devices 1|
|Desktop PC|-|                                  |                               |  |---------------|
|----------| | |------------|                   |                  |----------| |--|other devices 2|
             |-|DDwrt Switch|===={ Homeplug ={=====}= Homeplug }===|  Router  |-|  |---------------|
|----------| | |------------|                   |                  |----------| |--|other devices 3|
|  Server  |-|                                  |                               |  |---------------|
|----------|                                    |                               |--|other devices 3|
                                                |                                  |---------------|

Problem is, if my server wants to speak to my Desktop PC, I reckon it has to run everything back and forth to the router through the homeplug (which has a dodgy low connection speed).

Ideally I want some kind of subnet where the DD-Wrt Switch could handle DHCP for the Desktop PC and Server so they can talk directly, but then also be able to get LAN access from the router on the other side of the homeplug... and also the internet that arrives at that point.

I'm in a total language vacuum however, I don't know what to google to start reading, I've tried 'subnets' and 'multiple DHCP' but I don't know enough terms to get started.

Could anyone tell me:

• How best to describe what I'm trying to do (so i can google from there)
• Am i perhaps not finding anything because I'm trying to do something totally stupid
• Would anyone have any specific recommendations re-DD wrt?

Extra Info

• I do have admin access to the central router, so I can change settings there

• The central router does not run DD-wrt and i'm unwilling to flash it

• I have access to an additional TL-WR841N that could run DD-wrt if needed

Any pointers would be much appreciated.

Answer 1

You are incorrect in assuming that data from your desktop PC to your server has to transpose the network to the far end router and back, it does not work that way. The DD-WRT router is acting as a switch (not a hub), assuming a simple host to host interaction, the connection between your desktop PC and server will not leave the DD-WRT router (switch) except to the ports which are connected to each device.

What you have here is one large broadcast domain, broadcast packets will tranpose the entire network, not normal host to host (IP address/MAC to IP address/MAC) communications.

If your connection speed is slow, and DD-WRT is doing it's job handling the switch functions, the cause of your lag/slowness is somewhere else.

If for some reason the DD-WRT device is acting as a hub, not a switch, that could be the issue... but unless your DD-WRT device is EXTREMELY old, that is not the case.

And the configuration you are asking how to set this up with two subnets, two broadcast domains, or two networks, in this case the references are all basically the same. But I doubt this is the answer to your problem.