ADSL2+ dropping to ADSL_G.dmt

jaydev · 04-01-2019 12:05AM #1

Been having a merry old time over the last 2 years with eir broadband.
Now on Vodafone and continuing to try - so having to still rely on eir.

They tell me my line can achieve 20mbps - after a couple of engineer visits; they never actually say if they did anything at the pole or exchange.

I've recently tried both the Vodafone and old D1000 modem - I like the better log info on the D1000.

All I am seeing in logs that I recognise as an error is the "ERROR Couldn't increase MRU to 1500" message.

The DSL takes a while to come up, then internet flashes a while trying and eventually both go off and try again.
Whilst they are trying I get status on the box of 'Connected' 'ITU G 992.5(ADSL2PLUS)' '18554 kbps/765 kbps' '13.7 dB/ 4.5 dB' which seems to me that a connection is established over ADSL2+ at around 18mbps but this doesn't hold and the line is dropped.

Eventually I get a stable connection at 'ITU G 992.1(G.DMT)' '7616 kbps/768 kbps' '8.5 dB/ 5.0 dB'

..so seems to be dropping back to ADSL_G.dmt

Can anybody suggest anything I can spot in the logs that might help me work out if this is a problem on my side or some problem with my profile in the exchange?

For extra info I'm around 1.2km from the exchange - so the engineers telling me I can get 20mbps seems about right.

Both modems tried with default settings.

Thanks for any advice and suggestions.

Marlow · 04-01-2019 01:17AM

MRU and MTU should not be higher than 1480 .. maybe 1492 .. your router has an MTU of 1500 and 8 bytes are needed for Pppoe, so 1492.

But that shouldn't have anything to do with your issues.

/M

ED E · 04-01-2019 01:21AM

Your upstream sucks. 4.5dB is equivalent to RTE via a weak AM signal.

The weak US will cause regular drops and the DSLAM will try and recover. If its failing regular enough this can cause an ADSL1 attempt to lock just out of pure chance.

Rule out internal issues then fire it back to OpenEir.

jaydev · 04-01-2019 10:47PM

The MTU on the router is set at 1492 so I'm not sure what is trying to set the MRU at 1500 to trigger that error message.
So can I assume this is something the router will handle without affecting the problems I'm seeing?

jaydev · 04-01-2019 10:58PM

Appreciate the response.

I can't necessarily say I've noticed unreasonably frequent drops.
So by looking at the data, the upstream is no better with either ADSL2+ and ADSL_G.dmt

..are you suggesting that ADSL2+ is less tolerant and therefore somehow the quality of the US is causing the DSLAM to retry up until a certain retry count and then try to negotiate on ADSL_G.dmt and this somehow accepts the poor US more so than the ADSL2+ and stabilises the connection.

Sorry, I'm just trying to get my head around the process that's going on so I can figure out where to take the conversations I'm likely to need.

Vodafone have said they've shipped me a new router that I'll get early next week, but I'm gunna still try a few experiments this weekend with the old D1000 and the more recent Vodafone HG659.
If it isn't the router, I'll have to go back to Vodafone and get them to chase eir for me again. But I can also try to catch one of the local Open Eir vans on the off chance the techie inside is having a good day and willing to have a conversation.

Thanks for all and any ideas and directions of investigation I can take.

jaydev · 08-01-2019 09:30PM

So I got my replacement modem today.
Connected all up with no changes to settings.

Took around 25mins to sync up without dropping the dsl and again landed on ADSL_G.dmt rather than ADSL2+.

No change to speed tests and pretty much the same figures from the dsl connection details page - this is all as I expected it would be.

So now of course I have to ask for another line test to be completed - but when eir do that, they will do so without my knowledge and provide me with no details - and I'm not even sure vodafone sees the test data - so wondering what the point really is, but will have to follow the process yet again.

Just as an option - how would I go about performing a line test on my side? i.e. how do I test that my wiring from my master socket to the pole is actually in a healthy state? I haven't a clue how I would do this without again having to rely on the same companies (eir and vodafone) that can't so far figure it out.
Do private companies do this sort of thing? I just can't see how I would get up the pole to check my wires as they terminate into eir infrastructure.

ED E · 08-01-2019 11:43PM

Line tests are done by the MTAU in the exchange. Unless you wanna drop a few grand on a meter you can't do far end tests.

Took around 25mins to sync up without dropping the dsl

This is all they need to know. Sync should happen in 90s. Even if you didnt have a vodafone account it would sync in that timeframe.

Unless you've got a DSL filter (https://images-na.ssl-images-amazon.com/images/I/31sHJZmrN-L._SX425_.jpg) where you shouldnt its up to them.

ADSL2+ dropping to ADSL_G.dmt

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