I'd start here - it's saying that the external interface is down. Whilst that's down, you're always going to get PADO timeouts.

In reply to a post by shyslop:

May 5 06:07:54 miniupnpd[2218]: Cannot get IP address for ext interface . Network is down

That message is very early in the output though; so it could be a red herring - however there us no message saying that the network has come up, and with the interface taking a 169.254.y.z address it would seem to confirm the interface is down.

In reply to a post by JonRennie:

That message is very early in the output though; so it could be a red herring -

I think that is a red herring, the upnp daemon is trying to set itself up, but before the public IP has been obtained by PPPoE.

My ASUS is no longer using PPPoE (as I switched to cable) but I think miniupnpd gets restarted when a public IP arrives.

Could be cabling, but most likely authentication issue.

In reply to a post by JonRennie:

however there us no message saying that the network has come up, and with the interface taking a 169.254.y.z address it would seem to confirm the interface is down.

There should be a link/activity light for the WAN port somewhere on the router; OP could check to see if its solid/blinking i.e. the link has come up.

At the other end of the cable, there is the "Port 1" LED on the ONT to confirm that the physical link is OK.

What are the options in the PPP Authentication box (screenshot 2)?

On my AX88U I don't have this option (probably because I'm running Merlin f/w) although mine is running fine with an ONT on BT Residential.

I assume you are a BT residential customer not business? I have on the back of my mind you need a different username.password for business.

In reply to a post by adrenalize_:

On my AX88U I don't have this option (probably because I'm running Merlin f/w) although mine is running fine with an ONT on BT Residential.

I'm an AX88U with Merlin (386.4) although on Virgin Media, so not using PPPoE, but if I change the type to PPPoE that box appears and I can choose Auto, PAP or CHAP.

I can't recall which one is needed for BT authentication?

Hmm, it's CHAP in the logs when mine connects. I'm on an older build of Merlin - which would explain why I don't have the option.

Thinking a bit more about it I think the PPPoE negotiation is before the authentication in the following PPP negotiation - so the PAP/CHAP settings and username/password are irrelevant as its not getting to that stage.

I have seen a couple of suggestions that either the previous PPPoE session is still active and the Asus can't cope with that (the BT Hub may cope better, well it obviously does) or that the Asus implementation is poor - some details in this thread https://www.snbforums.com/threads/unable-to-establis...

Not sure why some people's connect OK unless we are all on older firmware.

Yes you are correct. It is failing in the Discovery stage (PADO message not received) and not getting to the latter Session stage (PPP negotiation).

Huawei summarise the PPPoE process steps quite well on their support page here.

Is it a stale session (that the Asus is failing to clear) or back to Jon's point above - is there a problem with the link (that the Asus perceives)?

Edited by Pheasant (Wed 12-Jan-22 23:47:54)

Thank you all for looking into this, really appreciate it! Delayed reply as I was running some tests.

Firstly, yes it’s BT residential.

As for the connection on Asus:
- WAN light on the router is solid red, LAN light on the ONT is green (occasional blinking)
- Asus web interface goes from ‘cable unplugged’ to ‘disconnected’, so seems to detect something
- Tried all 3 options in the ‘PPP Authentication box’ but no joy

Some further testing:
I remembered I have a RPi with Openwrt, so tried but it also didn’t connect and got the same PADO error in the logs. It also didn’t work connecting my Mac to the ONT (but no detailed error message there).

It seems very odd to have these issues, yet the SH2 is working just fine whenever I plug it back in.

In all honesty I’m tempted to return the Asus and see how I get on with the SH2 for now. Happy to do more tests though if you have theories. Thanks again!

So the issue isn’t necessarily with the Asus router - the fact that it’s not working with either of the other two other devices directly connected.

Shouldn’t really make a difference, but have you tried powering off the ONT, leaving it off for 10 minutes, then powering it on again and then trying to connect with a ‘new’ device (not the SH2).

Otherwise if the credentials are correct, then the only other possible explanation is the PPP server on BT’s side - so that would be my next port of call: raising a support case - as you should definitely be able to connect using your own kit.