Help identify network issues

[Sandro797]

Here's my network setup. From modem cable goes to TP-Link WR940N (for downstairs usage) and from this router, the cable goes to TP-Link WR841N (for upstairs usage), which is connected to PC via Ethernet cable. For 3 years the cable from 940N was plugged into the WAN port of 841N. About a week ago, I asked on this forum how to connect to my TV which is connected to 940N and followed an advice to plug the internet cable (coming from 940N) into LAN port on my 841N router. Everything worked fine, but after starting a game (Rainbow 6 Siege), it froze for 30 seconds and gave me a connection error. However, I was able to alt+tab and open different websites. I thought that it was this particular game that had problems, but almost same happened to other game from other developer (World of Tanks). In-game network meter went red and I could not move. My friend was in the match with me and he did not encounter such problem. I tried restarting routers, flushing DNS, changing DNS, but nothing helped. I also tried to plug the internet cable back to my WAN port, but in this case, I had no network at all.

Any ideas about what can cause this issue? Or why can't I rollback to previous setup?

[WereCatf]

11 minutes ago, Sandro797 said:

and followed an advice to plug the internet cable (coming from 940N) into LAN port on my 841N router.

Did you disable DHCP-server on the 841N? If not, then both your routers are fighting over which one gets to serve DHCP-requests.

[Sandro797]

41 minutes ago, WereCatf said:

Did you disable DHCP-server on the 841N? If not, then both your routers are fighting over which one gets to serve DHCP-requests.

I can't even login to 841N anymore. Before cable swap, I used 192.168.0.1 for 940N and 192.168.1.1 for 841N. Now only 940N login works. When I type 192.168.1.1 it gives me a different login page called Residential Gateway, which is my main modem.

Edited September 26, 2018 by Sandro797
Found Residential Gateway login/pass on main modem

[Alex Atkin UK]

That is correct, you'd need to disconnect the 841N from the other router, connect to the 841N, disable DHCP, plug it back in.

 

If you want to still be able to access the web UI on the 841N you'd also need to change its IP address into the same range as the main LAN first (ideally changing the main router to exclude that IP address from the DHCP range so it doesn't accidentally conflict), otherwise you will only be able to access it again by manually setting your PCs IP address into the correct 0.x range.

[Sandro797]

1 hour ago, Alex Atkin UK said:

That is correct, you'd need to disconnect the 841N from the other router, connect to the 841N, disable DHCP, plug it back in.

 

If you want to still be able to access the web UI on the 841N you'd also need to change its IP address into the same range as the main LAN first (ideally changing the main router to exclude that IP address from the DHCP range so it doesn't accidentally conflict), otherwise you will only be able to access it again by manually setting your PCs IP address into the correct 0.x range.

I watched a video on Youtube where all that was explained. Now I can access both routers. Also I disabled DHCP on 841N and tried to play R6S, but after some time, same thing happened. Screem froze and I got kicked to menu receiving a connection error. Discord worked fine at that moment. My voice did not distort at all.

[Alex Atkin UK]

So both the main router and the PC you are having problems with are plugged into LAN ports on the 841N, right?

 

If so, this would suggest the problem is not with the 841N at all as its effectively being bypassed entirely as the LAN ports usually are a hardware switch semi-independent from the router itself.

 

I'd be checking the 940N is on the latest firmware or other issues there.  To be absolutely sure you can always plug the cable straight into the PC from the 920N but it shouldn't behave any differently.