How to make VoIP (SIP) Phone work on Bridged ISP Router?

Installing and Using OpenWrt
1

Hello guys, I need your help! For the past 2 days I've been trying to set up my new OpenWrt router (Linksys EA8300) to work behind my ISP Router.
My ISP Router is a Zyxel VMG8828-B50B, it's a branded Router from my ISP (WINDTRE), it should be very similar to the Zyxel VMG8825-T50K.
This is my current setup:

Setup
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I managed to put the ISP Router in Bridge mode, but my Analog Phone no longer works. How can I fix it?

This is how I put the ISP Router in Bridge mode (sorry but I have to use imgur, since I can't upload more than one media on this post):

Broadband config

I don't know if I should let the VLAN option enabled as is or not. With it enabled I can get Internet working on OpenWrt. If I disable it, Internet no longer works, even if I make the 835 VLAN on OpenWrt and assign it to the WAN Interface (I don't know if I'm doing it correctly to be honest, even tho I tried to follow the documentation).

I think with my current setup I can do one of the following configuration (from best to worst):

  1. ISP Router in Bridge mode, let OpenWrt Router handle the PPPoE authentication and everything else;
  2. ISP Router in Routing mode (Default), use PPoE Passthrough (I have no idea how it works, I tried setting it up but apparently I can't get it to work, I don't know if I misconfigured it or if my ISP doesn't allow more than one PPoE session);
  3. ISP Router in Routing mode (Default), connect the OpenWrt Router with a Static IP address, in this case I'll get double NAT, so to get around it I'd set a Static Route on the ISP Router to the OpenWrt Router and disable Masquerading on the WAN Firewall Zone (is this right?).

Are there any other possible configuration? What is the best (ideal) configuration?
From what I understand the 1st one would be the ideal configuration, since the ISP Router would act as a dumb Modem and I'll be able to do all the configurations on OpenWrt to my liking.

The 3rd configuration would still be acceptable, but how would I go about portforwarding? In that case it should be done on the ISP Router, right? If that's the case I'm not a big fan of it, I'd like all of my configurations to be centralized on one device (OpenWrt Router).

From what I read online, different ISPs handle VoIP in different methods. I don't know how my ISP handles it.
I'll leave some more screenshots of the VoIP configuration:

VoIP config

Thank you for your help!

P.S.: When the ISP Router is set in Bridge mode, the INTERNET led shuts down (Normally it would be green = Internet working, red = Internet not working), is this the intended behavior? I guess so. Meanwhile the PHONE led becomes orange (Normally it would be green = phone working, orange = phone not working). Would it turn green if I were to make it work? I guess I'll find out.

P.P.S.: I forgot to mention I'm using my ISP's DNS settings (for now) so I can resolve the domain "voip.windtre.it"

2

Ok, quick update: my ISP doesn't allow more than one PPoE session, so I can't use PPoE Passthrough.
I found this information reading a forum post online, I also tried again to set it up and I managed to get it working, but as soon as the OpenWrt Router authenticates then the ISP Router loses the Internet connection.

Regarding this:

I think I got it now, of course I have to let the VLAN option enabled on the ISP Router to get Internet working. I got confused about this point because I was reading this: [OpenWrt Wiki] ISP Configurations. But that assumes there's just the OpenWrt Router without the ISP Router.

So.. how should I go about getting my Analog Phone to work with the ISP Router in Bridge mode?
From what I understand, I need the VoIP credentials (I'll ask my ISP about them), but where do I put them? Do I need to set up Asterisk? [OpenWrt Wiki] Asterisk
Do I need to connect the Analog Phone in another way? Because right now it's plugged in directly in the ISP Router, but I don't know if that's how it's supposed to be connected.

Also, is there a way to get some logs or error message? Because right now, all I see is just the SIP Line being unregistered on the ISP Router, and if I try to manually register it it just fail to do so without saying anything. I tried looking on the Log section of the ISP Router but it's just empty, I even tried looking in the Browser Console (maybe they're psychopath lol), but I can't find anything. Because right now I don't actually know what I'm looking for.

Thank you for your help.

3

It sounds like the phone can't work unless the ISP router can route it using an address obtained from the ISP via pppoe. So since only one such address is available you can't have another one on your router.

If you know the SIP credentials you may be able to use your own ATA box (Analog Telephone Adapter) or SIP phone after your router. The ATA in the ISP box would not be usable.

4

Hmm.. ok, so let's say I get a SIP Phone, how should I set it up?
I'll connect it to the OpenWrt Router and then set up Asterisk with the SIP credentials from my ISP? Is that the correct way?

5

Asterisk is a SIP server. It isn't needed when using someone else's server. You would configure a phone so that it logs in to the ISP's server.

6

Oh ok, yeah that's why I had some doubts. So how would I go about configuring the SIP Phone? Like where do I put the SIP credentials? Is it something you configure directly on the SIP Phone itself, or do you configure it through OpenWrt? Sorry but I'm a bit lost on this part.. Thank you :slight_smile:

7

did this one before but with my pfsense.you need to have your isp sip server/gateway and your sip account and also sip phone ( i used yealink ).and i took all that information on my isp provided router

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