Unable to establish multiple PPPoE sessions

Yota

Very Senior Member
There are two errors here both related to multiple PPPoE connections:

Long story short:
Features not working:
PPPoE relay
run multiple pppd

Working function:
Two PPPoE sessions in dual WAN


The first error is that the PPPoE relay cannot work. I discovered this problem for the first time in 2018. Since there is no need to use this function, it has not been carefully investigated before. This time, it is confirmed that it is an unexpected behavior after careful investigation.

Steps to reproduce:
1) Enable "PPPoE relay" in "WAN" - "NAT Passthrough"
2) The router establishes a connection through PPPoE
3) The computer is behind the router LAN using PPPoE to establish a second connection

What happened:
When the computer successfully establishes the PPPoE connection (the computer can access the Internet normally through this connection), the router PPPoE connection will freeze and cannot ping any external IP address, but the PPPoE of the router does not show disconnection, the network map still shows the WAN IP address obtained through PPPoE, it doesn't even think the WAN is disconnected, there is no error in the log, but it can be confirmed by other devices connected to the router and SSH that the Internet is no longer connected at this time.

What should happen:
The router's PPPoE session remains connected while allowing the computer to establish a second PPPoE session.



The second is the function I need

Background:
I dropped all the IoT devices in my house into guest network 1, I am happy with their separate subnet, now I want to establish a new PPPoE session and add that session to the bridge where the guest network is, so the guest network and my personal network will have completely different external IP addresses, and the network bandwidth they are using will not affect my personal PPPoE session (my ISP assigns independent bandwidth limits to each PPPoE).

Before starting, I tested whether my ISP supports multiple PPPoE sessions, the test is very traditional, plug the ISP-provided WAN cable into the switch, make a PPPoE connection through both computers under the switch, and see if they can get it to a different IP address and have internet access, the answer is yes they can.

Then I plugged the two cables from the switch into the router's WAN and LAN1, and enabled the multi-WAN feature, and they both worked fine. It's just that I need to modify the mac address of the second WAN to avoid conflicts.

What did I do:
1) Router WAN establishes connection (no multi-WAN)
2) Copy the /tmp/ppp/options.wan0 configuration file required for the PPPoE session, and edit the linkname in it to avoid conflicts.
3) Run the second pppd process with the following command
Code:
/usr/sbin/pppd file /tmp/ppp/options.guestwifi

What happened:
Using the ifconfig command, i can see that both ppp0 and ppp1 sessions have been successfully established, and different IP addresses and different gateways have been obtained.
However, but at the moment the router's WAN again loses internet connection, can't ping any external IP address, no internet connection, just like that problem above.

Expected behavior:
The successful establishment of the second PPPoE session will not cause the first session to freeze or be interrupted. So I can add ppp1 to the guest network.



Models: RT-AC68U and RT-AC86U (full reset, only set PPPoE username and password, without any other settings)
Firmware: Asuswrt-Merlin 386.7_2



My suspicions:
Possibly the internet connection is lost due to a change in the router's routing policy after the second PPPoE session is established, but I don't know how to justify this guess, I'm just guessing.
 
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Yota

Very Senior Member
Can anyone point me in the direction of solving the problem? What can I do to determine if the problem is coming from the pppd process or something else? Or does this rely on Broadcom's switch drivers?
 

DJones

Senior Member
Can anyone point me in the direction of solving the problem? What can I do to determine if the problem is coming from the pppd process or something else? Or does this rely on Broadcom's switch drivers?
are you running the same pppoe account on both WAN? It could be a limitation of your isp that only one connection can be made at a time.

“(my ISP assigns independent bandwidth limits to each PPPoE)”

I assume by this that’s not the case.

I also assume your not enabling Dual Wan from the UI. As that in my mind maybe could be causing 3 pppd sessions to be made, and if your isp limits connections to one per pppoe account and you have 2 accounts then the 3rd connection could be causing the disconnection.

7C1F18D5-56DB-4A92-BCB8-88F69FA9DED4.jpeg
 
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Yota

Very Senior Member
First of all thanks for trying to help me

are you running the same pppoe account on both WAN? It could be a limitation of your isp that only one connection can be made at a time.

Yes, I only have one PPPoE account, but my ISP doesn't restrict using that account to log in multiple times at the same time, however there are some limitations there that I think come from the PPPoE server's software, like devices that are logged in at the same time must have different MAC addresses.

“(my ISP assigns independent bandwidth limits to each PPPoE)”

I assume by this that’s not the case.
It doesn't matter because I'm happy with the speed, even two PPPoE can't break the 1Gbps Ethernet port limit.

I also assume your not enabling Dual Wan from the UI. As that in my mind maybe could be causing 3 pppd sessions to be made, and if your isp limits connections to one per pppoe account and you have 2 accounts then the 3rd connection could be causing the disconnection.
No, I was just testing when I used dual WAN and two computers under the switch, the dual WAN was designed to test if the router could allow two PPPoE processes, and the two computers under the switch are to test whether my ISP supports logging in with the same account at the same time. the answers are all yes.

When these tests were done, I restored the router to factory settings, then configured it as originally described, and found the error.
 

Yota

Very Senior Member
:)Hopefully someone out there can reproduce the problem, as it's very easy to reproduce, just enable the PPPoE relay and make an PPPoE link again with the computer and it will trigger.
 

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