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[aesmith]

I realise this might be an unusual idea, but I'm considering using by AA L2TP account over Starlink for normal operation, to get around CGNAT issues. However I'm keeping my AA ADSL for the meantime, as failover if Starlink goes down. Anyone do anything similar? I think I would need to configure things so in a failover situation it doesn't try to connect to L2TP over the ADSL, which I presume would fail.

[Alex Atkin UK]

Not really unusual, its the exact reason they sell the L2TP as standalone if you don't have them as your ISP.

The problematic part is if you are using your ADSL L2TP connection, you can't be connected to ADSL and L2TP at the same time.  You'd need to either make sure PPP is only brought up on ADSL when Starlink is down, or pay for a second L2TP connection.

[aesmith]

Cheers. In testing what seems to happen is that L2TP takes priority at the routing level. When it's up the ADSL stays up, but any traffic either gets binned at AA, or maybe return traffic does. Either way traceroute shows just one hop after my router. As soon as I disable the L2TP then routing via ADSL immediately resumes, no retrain or anything needed.

But that was a short test, I dont know whether leaving L2TP up would cause the ADSL to drop PPP at some point.

[Chrysalis]

As far as I know if you have a broadband account with AAISP, it can also be used as L2TP, so if you are prepared to keep the ADSL disconnected (not the sync just the PPP auth) whilst the Starlink is online you can save a bit of money.

Then when the starlink goes down, login to the ADSL using the same details.

[aesmith]

I need to test a bit more but at the moment it seems like ADSL can stay up, with PPP logged in, even while I am logged into L2TP. It just doesn't route. Then when L2TP drops it immediately starts routing with no intervention needed.

I need to test whether it stays "waiting" like that indefinitely, and also whether it will restart after a retrain or power cut and resume "waiting".

But also need to find some way of stopping the L2TP trying (or succeeding) to reestablish over the ADSL when Internet fails over.

[Alex Atkin UK]

I need to test a bit more but at the moment it seems like ADSL can stay up, with PPP logged in, even while I am logged into L2TP. It just doesn't route. Then when L2TP drops it immediately starts routing with no intervention needed.

Its very smart if AAISP has implemented it so L2TP always takes priority.  Having the end users router in control (by simply dropped L2TP if the main connection is working) is a very graceful way of doing it.

[aesmith]

I'm missing the obvious. I'll just ask Andrews and Arnold whether this is expected behaviour and can therefore be relied on. I'll do a few quick tests first, for example rebooting the ADSL.

[Chrysalis]

Please let us know how they respond, as I am curious also.