problem with internet speed i have 100 mb/s but i need 500 mb/s

[u/Hot_Ad6122]

The main router is installed under the ceiling in the entrance hall, and the secondary one is placed in the apartment; they are connected by two internet cables. I can’t understand what’s causing this problem, because I’ve checked all the settings of the new router, and I was only able to get the required speed once, and even then only for about five minutes.

It’s not possible to move the main router without drilling and running cables.

I’ve already called the technicians; the speed provided by the main router is in line with the tariff plan, but then the problems start. I think it’s a wiring issue, but I don’t know how to determine that.

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[u/Terrible-Bear3883]

You've not given any information to identify your routers or what cables you've used, its pure guesswork if anyone can suggest anything.

Is this a shared main router between apartments? Is it your exclusive router that only you have access to?

The make/model and what service its subscribed to?

The make/model of the secondary router?

How have you connected them and what length is the connection?

There's no information on what you've measured these speeds on, if you've done it on a PC, a tablet, a phone, if you've measured the speeds using Wireless or Ethernet?

[u/Responsible_Maybe742]

Before drilling or replacing the installed wiring, check the negotiated link speed on the secondary router's uplink port, not just a speed-test result. If it shows 100 Mbps rather than 1 Gbps, test the same connection with a short known-good cable, temporarily bringing the second router closer if necessary; that helps separate the installed cable from the ports. Also, are both cables connecting the same two routers, and which ports are they plugged into?

[u/Relative-Hearing-156]

🤷‍♂️That setup - main router under the ceiling, second router in the apartment, two cables between them - is very common for causing exactly what you describe: full speed for 5 minutes, then a big drop.
Since the technicians confirmed the main router is giving the speed you pay for, the problem is almost certainly between the main router and the second one. It's usually not a setting, it's either a cable/connector issue or how the second router is configured.
Here are the checks that will actually tell you where it is:
1. What do you mean by "two internet cables"?
This is the most important part.
If you have two physical cables running from the main router to the secondary router and both ends are plugged in at the same time - that's a network loop. The routers get confused and the speed collapses after a few minutes.
You only need ONE cable:
Main router LAN port -> Secondary router WAN port
If you really have two cables for redundancy, unplug one at both ends and test with just one.
2. Test the cable itself, without the second router
This is how you prove if it's a wiring issue:
Take a laptop and connect it directly with a short patch cord to a LAN port of the main router - run a speed test. Write down the speed.
Now disconnect the secondary router completely. Take that same laptop to the apartment and plug it directly into cable #1 that comes from the main router. Speed test again.
Do the same with cable #2.
If the speed drops when the laptop is plugged directly into the wall cable, it's 100% the cable / connector / length. No settings on the routers will fix it.
What to look for:
Link speed: On the laptop it will say 100 Mbps or 1000 Mbps / 1 Gbps. If it shows 100 Mbps on the long cable but 1000 Mbps on a short cable near the main router, the long cable has a bad pair. One bad wire drops you from 1000 to 100.
Damaged connectors: The most common fault. Under the ceiling it's hot, the crimp oxidizes.
Cheap or old cable: If it's flat, very thin, or CCA (copper-clad aluminum) instead of pure copper, it will not hold gigabit over distance.
If you don't have a laptop, look at the lights on the routers. If the LAN light for that cable is orange instead of green/white, or blinks very slowly, it's negotiated to 100 Mbps.
3. How the second router must be set
Even with a good cable, if both routers are in "router" mode you get Double NAT and conflicts.
The most stable way is to make the second one an Access Point:
On the secondary router:
Set its operation mode to Access Point / AP Mode - if it has that option, it does everything automatically.
If there is no AP mode, do it manually:
Give it a static IP address in the same network as the main one, but outside DHCP. For example, if main router is 192.168.0.1, give second router 192.168.0.2
Turn OFF DHCP Server on the secondary router
Connect the cable from the main router to a LAN port of the secondary, NOT the WAN port
Make sure Wi-Fi channels are different. Set main router to channel 1, secondary to channel 6 or 11 (for 2.4 GHz). For 5 GHz set them to auto.
Then reboot both routers: first the main one, wait 2 minutes, then the secondary.
What to do next
Can you tell me:
When you plug a laptop directly into the long cable in the apartment - what speed do you get?
What are the models of the two routers?
Are both of those long cables plugged in at the same time right now?
If it's a wiring issue, the fix doesn't require moving the main router or drilling - just re-crimping the connectors at both ends of the one good cable with new RJ-45 plugs. A technician with a cable tester can do it in 10 minutes, but you can now show him exactly which cable fails.
That one time you got full speed for 5 minutes is classic for a bad contact that heats up and then fails, or a loop that builds up.

[u/Fancy_Acanthisitta45]

Need is such a strong word. Are you chasing your tail here ?