Strange addresses showing up without logging into ISP

When an adsl modem is connected up to a phone line with adsl, it quickly establishes sync, sync light is lit.

Then it is set in interface to automatically check the adsl type of connection - LLC, VCMUX, PPOA/E - what happens is that after a short while it says PPOE/LLC and then without providing login details it shows this -

IP address 172.16.67.78

gateway 81.146.177.7

dns 62.6.38.125

and the light meaning connected to internet is lit, but doesn't blink as would be case with data transfer. In fact nothing can be done, ping trace etc.

But why is this occuring?

172.16.67.78 is in one of the three private LAN address ranges. (so OK)

81.146.177.7 shows the ISP as being BT. (and is, presumably, a BT gateway)

62.6.38.125 confirms the ISP as BT (and is a BT DNS server)

So, all seem valid, so far.

yes I know about the 172 private range. And I looked at what the others were.

They may be valid in themselves, but why are they showing up?

The adsl provider is not BT.

Is there some crossed line in the exchange?

There have been recent problems when the normal router is used, sync losses, low speed, timeouts of DNS lookup.

This was a different modem tried to see what wqs going on. Freshly reset to its new defaults.

I guess the way it determines the type of connection is by trying them, and this results in it getting the info shown. A BT wholesale circuit, presumably.

The adsl provider is not BT.

So who is?

How long since it went wrong?

Your adsl login settings are correct aren't they?

Sounds like some form of walled garden.

There are _no_ login details. The adsl modem is at reset default. It's only job is to see what the stats are without trying to actually login to the ISP and somehow it ends up showing that info I described.

The sync is established. The page on the modem for details has a "wizard" to check what type of adsl as I said. It tries 8/35 0/38 VCMUX, LLc PPOE/A.

After some seconds when it says that PPPOE/LLC is correct the address details appear.

I'm intrigued to know why its front end should be given a private non-internet address but with gateways and dns related to BT.

In reply to a post by yarwell:

I guess the way it determines the type of connection is by trying them, and this results in it getting the info shown. A BT wholesale circuit, presumably.

I don't know if there's a catch22, egg/chicken thing here

But, should this happen? If there's a circuit at the exchange that somehow is getting to a BT junction before it goes to the proper ISP's junction. I don't know enough about tech to explain that properly. I think that they are all fed by BT at major hubs somewhere down south but what's a t the exchange should be somewhat different, yes no!

something to do with authentication maybe. Does it matter, is it important or is this just about being curious ?