Question Direct WAN connection fast but slow with any router connected ?

[r00ter]

I'm having a super weird issue with my home network and am out of ideas of how this could even be happening. The other day my network started being so slow that it's barely usable. My setup is as follows: Cable modem -> patch cable -> router. Now if I connect a laptop to the modem directly, I get 70Mbps. But as soon as I connect a router (and by "a router" I mean either my Turris Omnia or Archer C2 v2 with Gargoyle), I only get like 0.5Mbps, no matter if I use 5GHz, 2.4GHz or a LAN port (with WIFI physically disabled on the router).

I did factory reset the cable modem, factory reset the Turris Omnia, reinstalled Gargoyle on the Archer C7, etc. Tried different pach cables and ports as well. But no matter what I do or which router I connect to the modem, every time the connection passes through one, it's becoming so slow that it's pretty much unusable. It's as if the ISP would detect what I plug into the modem and throttles the connection as soon as a router is plugged in. It doesn't make sense because both routers worked just fine up until the day before yesterday and I can't figure out any reason that would make sense. Does anyone have any ideas?

 

[Ralston18]

There should only be one device acting as a router.

You have three devices working as or potentially working as routers:

1. Cable modem (ISP, make, model) ?

2. Turris Omnia

3. Archer C2.

Which one is the main router that provides DHCP IP addresses to network devices?

What is the physical network configuration (line diagram example where ----> represents an Ethernet cable.

IPS === Coax, DSL, Fiber ===> Cable Modem ---->[WAN Port]Turris Router ---->[LAN Port] Archer Router [LAN Ports} ---> wired network devices and ~wireless ~> Wireless devices.

Edit and correct my line diagram as necessary.

What IP addresses are being used by the routers and other network devices?

Also, on your computer run "ipconfig /all" (without quotes) via the Command Prompt.

Post the results.

 

[r00ter]

It just randomly started to work again about 40 hours after the problem first appeared. Must have been related to the ISP somehow, although I still have no idea how.

 

[Ralston18]

That is good.

Take a look in Reliability History for error codes, warnings, or even informational events that may have started just before and then stopped just after that 40 hour period.

Reliability History is user friendly and uses a time line format that can be very revealing.

Another place to check is the router's logs provided logs are available and enabled.

Just in case.....