Losing all of my bandwidth between main and "switch" router

Question

My parents live in a house where one router just can't supply the entire space with wifi. To resolve this, we use a D-Link router that was lying around in "glorified switch" mode.

That sounds reasonable, but in practice, whenever I'm connected to the SSID associated with my switch router, I go from 15MBPS on the main router down to <2MBPS consistently. I've spent half the morning trying to troubleshoot this, but no luck so far.

I've been able to notice a few things that may help with troubleshooting:

• It seems like the DHCP server is disabled on the secondary router (good news for the "glorified switch" theory, I guess), since all the routing seems to be happening through the main router, even when connected to the switch router. To determine this, I ran a quick traceroute to an external address, and the first hop is through my main router's IP, not the switch one's.
• I am totally unable to to connect to the admin page of my switch router. My first thought was it's because both routers have the same default gateway IP, but no. One is on 10.0.0.138, and the other is supposed to be on 192.168.0.1. Unfortunately, no dice there.
• I tried to sneak out the IP address of the second router by checking the list of connected devices for the main one, but for some reason it's an IPv6 address that's entirely unpingable/unresolvable/inaccessible.

Are there any flaws in my troubleshooting logic so far? Can you see any glaring misunderstandings I have w.r.t how my network is setup? I am by no means even slightly conversant in networking, so please bear with me.

Thanks a lot for any help or advice! :)

Edit: We run some patching lines of unknown nature between floors in the house, and so far the switch router was plugged into a wall-mounted ethernet port. I just did a quick test to eliminate that variable by taking the switch router and plugging it straight into the main router, and who could have guessed it.. I get 10MBPS down on the switch router now, so 75% of my transmission loss is due to whatever it is we have running in the walls. I still have -5MBPS down compared to the main router, so I'll do a factory reset on the switch and make sure everything is set up correctly.

Edit2: OK so I've had the setup as configured by me running for a couple of days, and I've run into a bunch of weird behaviors:

• Sometimes I'd lose connectivity when on the "AP" wi-fi. When I switch networks and then back, I get a "password invalid" error. This has happened to me both on phones and laptops. After a while, it seemingly self-resolves
• My phone is getting assigned an IP in the 169.254.X.X range when on the secondary wi-fi network, which seems like bad news. Unsurprisingly, no internet access in that config. Again, DHCP server is off on the secondary router, and I've reserved a static IP for the secondary router on the primary.

Any advice for these new quirks?

Answer 1

The flaw I can see here is that the router and the switch are not in the same network segment.

While one is in 10.0.0.X, the other is on 192.168.0.X. Ideally, both should be the same segment, so no special routing is required. The switch could get its IP address from the router via DHCP or have a static IP address.

If you have difficulties entering the log-in page of the D-Link, you could perhaps connect via cable to your computer, both otherwise isolated from the network, then the D-Link followed by the computer. If the D-Link is still unreachable, perhaps a factory reset could fix the issue.

This is the most that can be said with the information you supplied. For better answers, you should specify the router and switch models, their setting that you might have changed, whether wired or wireless, and how you have measured the speeds.

Answer 2

Since it appears to be a wiring issue somewhere and not related to either router, this is where I'd start:

1. Check the patch cables you're using between each router and the wall. You can test them by plugging them in, one at a time, directly between each router like you did already when you were able to get a 10Mb download speed.

2. Replace each RJ-45 wall ports. You can get them at Lowes, Home Depot, etc., and they should come with a plastic punch-down tool. If the end next to your main router is a patch panel, you should be able to use the plastic tool to re-punch the suspect wires and if it doesn't work still you'll need to pull the cable out and redo it. If you do pull them out, you can also try moving the cable to a free port.

3. If one and two don't solve the issue, the problem might be with the cable in the wall itself and needs to be replaced. Could be a bent, chewed, cheap or otherwise damaged wire.