[Gllug] ADSL Puzzle

[Ken Smith]

Hi, I know that there are some folks here who have a in-depth 
understanding of how ADSL works. I'm trying to get a grip on a situation 
that has developed.

Following a power fail the ADSL link did not return. Looking closer,  
the ATM part is working showing 1152K down and 288K up. The noise 
margins are 30 db up and 29db down. All very good. But the PPPoA 
connection is never getting established. The login credentials have been 
checked, double checked with the ISP and still no joy.

The power fail in the area was fairly widespread and could have affected 
the BT exchange too. Does all their gear still run from 48V batteries 
these days?

 From here I'm not sure how things work. Seemingly, a bit of BT 
equipment claims that there was a failed login just after 8:00 this 
morning. Correspondingly the ISP's Radius server shows that login 
attempt as successful. Subsequent to that, I tried a different ADSL 
router with good and, as a test, bad login credentials. There were no 
traces of the login attempts from that router late AM today. The ISP say 
the line checks out OK and they can 'see' my alternative router and 
subsequently the original one on the end of the line.

So, it seems to me that finding out why BT's gear says the login failed 
and the ISP's Radius says it was successful seems to be the heart of the 
matter. How can that be? I'm assuming a message is returned by the 
Radius saying something like 'those credentials are good let the 
connection proceed'.

Or is this beyond hope and time to de-provision the circuit and 
re-provision it with a different ISP?

Any enlightenment most welcome.....

Thanks

Ken



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