CISCO EPC3208 modem and TP link routers - constant Internet disconnection

Hello,
I would like to ask for help regarding the cooperation of my CISCO EPC3208 modem with TP link WR340G and TP Link WR940N routers
My home network looks like I have a CISCO modem (toya), a TP link router connected to it (by cable) AND also a cable connected PC.
And for some time now, the Internet has been disconnected in this statement at completely random times. Modem works fine (I called Toyota several times and they saw no problems with the modem) - moreover, I connected the modem directly to the PC and it also worked fine (in the sense it did not disconnect from time to time).
Natomaist, after establishing a connection with the Router, the disconnection takes place every few minutes / hours (the lamp on the router lights up, which indicates that there is no internet). Every time when in such a situation the CISCO modem is restarted -> the internet appears temporarily and then the fault returns.
In the end, I bought a new TP link router, I thought that the old one was used up after a few years - but the fault has not disappeared.
I rummaged through a dozen or even tens of forums to find a solution. Despite various treatments such as:
1.I changed the cable connecting the PC with the router
2. I changed my DNS setting to 8.8.8.8
3. I turned off DHCP temporarily
4. I colonized MAC
5.Changed my lan IP from 192.168.0.1 to 192.168.2.1
6. I have updated the firmware to the newest one dedicated to my new router
7. I restarted the whole set several times in the order Modem-> router> PC (with full shutdown and turning on in this order)
8. I uninstalled antiviruses and firewalls (it detected several worms)
9. I scanned for viruses before uninstalling
10.after uninstalling, I reinstalled the antivir and firewall and scanned again qksee virus detected -> removed
None of the above steps solved the problem.
I will be grateful for any suggestions - while writing this post, the internet broke down on me 3 times I'm really fed up.
The network card in the PC is: Realtek PCIe GBE Family Controller
The attachment also adds the status from the router and ipconfig

pitermxa wrote:

I would like to ask for help regarding the cooperation of my CISCO EPC3208 modem with TP link WR340G and TP Link WR940N routers
My home network looks like I have a CISCO modem (toya), a TP link router connected to it (by cable) AND also a cable connected PC.

in series or in parallel?

Draw the diagram, mark the ports on the routers.

Where is the second router in the diagram? select models.

Have you tried resetting the router to factory settings?

How old are routers?

Check the power supply:
- or take another power supply with the same voltage and equal or greater current efficiency
- or measure the supply voltage with a connected router and compare it with the rated voltage.

The story is that I started having this problem on the old WR340 wifi router and thought there was a kaput.
I bought a new WR940 and now tests everything only on this one.
It is probably not a matter of power supplies because both modems behave identically, but one WR940 is completely new. But I'll try to figure out a meter and measure it.

I also reset the router to factory settings.

Added after 32 [minutes]:

We managed to check - the power supply has 9V -> measurement 9.68V

pitermxa wrote:

Natomaist, after establishing a connection with the Router, the disconnection takes place every few minutes / hours (the lamp on the router lights up, which indicates that there is no internet).

Maybe I will ask what lamp exactly do you mean?

The second counter from the right -> if it is blue - the internet is there. When the internet fades it turns orange.

Have you replaced the cable connecting the modem to the router? There seems to be some switch from 1000Mb / s to 100Mb / s.

The mouthpiece began to appear with a completely intact set.
After buying a new router, I got a new ethernet cable in the set - so far it worked on the connection between the router and the PC. Now I swapped it with this one between the modem and the router. I will let you know if the connection continues.

Added after 1 [hours] 10 [minutes]:

The cable replacement did not help. I also replaced the cable between the modem and the router with another one. It keeps me disconnected all the time.

Try to use the TP-link as AP and check its stability.

The photos show that your physical connections are correct - the modem is connected to the WAN port of the router, i.e. the blue one. The router gets the network configuration from the modem or from the operator (the modem is "transparent"). I do not like this Google DNS, because it should be from the operator or second.
Yes, for full diagnostics, I suggest connecting the modem to the LAN ports (yellow) of both routers. Then the WAN port is bypassed and the router works as a normal switch with the AP. The lamps should permanently indicate the lack of internet. This corresponds to the direct connection of the modem to the computer.
I wouldn't mess with DNS 8.8.8.8 on my computer. Let the computer receive all network configuration from the DHCP server, i.e. the router. From the computer, you should be able to access the router's management panel via a browser. Then one part of the link is proven: PC - router.
Then something can be said after this additional diagnosis.
Do you have protected access to the router's management panel from the radio side? I will not pretend that I know the reason for your failure, but it reminds me a bit of a situation when a "parasite" joined the network via WiFi and fumbled with settings. Therefore, during the tests, turn off the radio link in the router.
Do you have access to the modem's management panel and does the contract with the operator allow you to change the settings?
Of course, do what the discussion participants wrote about before my post.
Krzysztof Podstawa

@pitermxa
Also RESET the Cisco modem with the button on its casing (30-second reset - you keep this button pressed for so long, then release and wait 10 minutes, Cisco will reset to factory settings and download the CMTS configuration again).

@ KOCUREK1970 - shouldn't I reset the modem informing my operator (TOYA) about it?

@kpodstawa - I will still test the switch mode - And I'll see.

In the meantime, an interesting thing happened. Something hit me and I connected my old worn-out Wr340 router for a while and it turned out that it started working, although in the week I do not have much time for testing (which is why I was not active on the forum), but I will try to load this old router a bit over the weekend and we will see.
On the other hand, it's very strange that this old router suddenly started working. Maybe you have an idea what happened?
I did not configure anything in it additionally as it was so I connected it and it worked.

pitermxa wrote:

KOCUREK1970 - shouldn't I reset the modem informing my operator (TOYA) about it?

No - you can reset the modem up to 300 times a day.
The operator does not condition when it can be done.

pitermxa wrote:

this old router suddenly started working. Maybe you have an idea what happened?

Maybe Toya has his MAC address entered in his database, or you cloned the MAC of your cable modem in this grandpa.

Hi,
Another unexpected situation happened over the weekend - the modem's power supply was burnt.
Perhaps the symptoms I described earlier were related to the fact that the modem's power supply was not working properly.
Unfortunately, I did not have another power supply that could replace the burned one, but today I will have a visit from a Toya technician and I will have a new power supply.
Then I will try to test both routers and let me know if the problem is solved.

Added after 7 [hours] 6 [minutes]:

After a few hours of internet load, I confirm that the problem was most likely a faulty modem power supply.
The topic from my side to be closed.
Thanks a lot everyone for the advice!