Fake bridge on my ISP router?

Installing and Using OpenWrt Network and Wireless Configuration
1

Hello guys! :face_with_peeking_eye:

I am supposed to be replacing an old modem/router combo at my relatives with something more up to date... I was thinking put the ISP device into bridge and connect an openwrt router , but I am running into an issue already on the ISP modem side of things - It's already set up as a bridge? ( Wtf? )

How do they have the internet working if it's in bridge mode already?

Connection looks like this :

ADSL cable ( Old phone cable - rj11 ) goes into > ISP Modem/Router combo , and from this unit you can connect via Wifi or Lan cables... They all work, phone has the internet and so does the TV

... are the devices getting IP address from the DHCP server on the ISP side ? ( Like the modem they provided works as a dumb Access Point or something ? )

I am not able to get you pictures atm ... But this is what I got to see over the video :

Under the "Setup interface" > "Internet"

Encapsulation mode :

*DHCP
*Static Address
*PPPOE
*Bridge - this is the one in use , I checked youtube and this is how you set the bridge mode?

Honestly idk how to check what's going on? I know about traceroute - check first 2 hops and see if it's a private IP but that's about it :cowboy_hat_face:

If you want the full background story it is kinda confusing - 3-4 days ago they received the modem and plugged it in but it didn't work for some reason , I went and logged in at that time and checked if PPPOE was enabled and it wasn't, the encapsulation mode was set to DHCP but the log was complaining about PPPoE - Something like pado sent and nothing received... PPPoE media channel error , or something... Should have saved it back then ....sigh

In the Internet status page it showed the router sending packages to ISP but it wasn't receiving any packages in return - like it was 100000+ packages sent and 0 received. ADSL status showed that the connection was fine at the time , packages were being exchanged between both ends

They complained to ISP and guess the ISP changed something on their side hence the need to put the modem in the bridge mode?

Now the Internet works but they lost a good chunk of upload speed from the promised 20mbps Download and 1mbps Upload :

They are getting | 15mbps down | 0.5mbps upload |

Maximum ADSL rate reported by the modem is | 21mbps download | 1.3mbps upload |

Do you have any tips for me when I call the ISP ? Ask them to revert all of this and give us a proper PPPoE connection ? To me this sounds like double nat on the ISP side already ( CGNAT is most likely in use ) ... if the router starts routing then it's a triple nat? :joy:

... Sorry it's just a wall of text , I'll attach pictures and traceroute in about 10hours from now

2

Could you clarify how this is related to OpenWrt?

3

... you can probably tell from the post that I don't have much clue about networking besides the very basic knowledge , that's why I am asking for some help to see how am I supposed to go about bridging this to the new router, are posts like these not allowed here?

4

Is anything running official OpenWrt?

5

New router? :melting_face:

6

Okay, I'm guessing that when you logged into the gateway from the ISP with PPPoE it was smart enough to put itself in bridge mode.

If your wan has a public ip address it is, indeed, passing your new router a public address.

You could DuckDuckGo your ISP gateway device and see if it mentions how to use it as a modem only if you want a full explanation.

7

Um, my understanding is that if it's in bridge mode internet should stop working until a proper router is connected?

It clearly says bridge mode yet the internet still works for all the devices connected to it?
( I am still not there at their house, so they are still using the ISP device only... )

The model is TD 8901N (TP-link)

8

Check the ip addresses assigned to the lan devices. If they are public, the gateway is just passing through public addresses.

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9

Thanks I'll check!

10

This is about all I can really help with and not because I don't want to help but because I'm not familiar with their ISP nor Gateway.

Your next step is to reach out to their ISP.

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11

First thing in the morning :saluting_face:

Ty for the help :blush:

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12

This is the OpenWrt forum -- it is a place that is focused on OpenWrt and closely related topics. Discussing random ISP related routers is typically off-topic unless it is, for example, being connected to an OpenWrt router.

Why is this? Two reasons...

  1. This is a focused forum. If it was a generalist networking forum, it would be very difficult for OpenWrt users to get the help they want that is specific and unique to OpenWrt. The forum would become overrun with all sorts of networking topics, resulting in a loss of the specific identity and purpose of this specific forum.

  2. If it was a generalist forum, the expectation would be that we'd know how to help with every different ISP's router, or the thousands of routers out there with their stock firmware. This is just not feasable. We focus on one thing (and things that are very closely related) and we do it well.

Therefore, you need to ask your question about your ISP modem/router device in forums that are suited for it -- be it the ISP support channels and/or forums that are either dedicated to that ISP or hardware, or generalist forums.

If you have difficulty connecting your OpenWrt router to other systems, we're certainly willing to see if we can help, but there is a limit to the depth of support for non-OpenWrt based devices.