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Author Topic: Line fault fixed, now lots of errors and issues (Resolved)  (Read 985 times)

spannerzone

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Line fault fixed, now lots of errors and issues (Resolved)
« on: October 09, 2020, 10:19:50 AM »

Hi,
Recently my BT phoneline suddenly got very noisy, impossible to make/receive phone calls and Plusnet FTTC internet sync dropped and was pretty much ususable, I've had totally stable FTTC at 73/17 for last 5 years.... Openreach finally came and fixed the trapped wires in the green cabinet that fed my FTTC, wires were getting grounded due to untidy install apparently. My Draytek 2762N now syncs as normal but I'm getting tons of errors reported and many sites cannot be accessed, such as any speedcheck site... Youtube is fine and plays without issue...it's just some sites that refuse to load.
As my line had a load of noise and I assume my modem caused errors while that fault existed, does a reset of something in the cabinet need to happen?

I've tried 2 Draytek 2762N and numerous ethernet connected pcs, all have same issue since this fault was fixed. I've got a dual socket phone/VDSL master socket so am sure it's not internal wiring, wifi or my equipment at fault. I've raised issue with Plusnet but hope someone might have some ideas on this?

Screengrab of modem stats attached...I noticed since taking that shot, Bitswap has now enabled itself, whatever that means.
« Last Edit: October 12, 2020, 11:46:01 AM by spannerzone »
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Weaver

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Re: Line fault fixed, now lots of errors and issues
« Reply #1 on: October 09, 2020, 10:41:25 AM »

Welcome to the forum, spannerzone.

If some websites consistently exhibit problems but not others then it’s nothing to do with your copper line or FTTC cab. You need to report this problem to your ISP. Are you using a wireless LAN ? If so then that could be the problem, so we need to rule that out first, so use an ethernet cable from your PC to your router and test various websites. If wireless does not seem to be the cause then report the problem to your ISP.

Don’t hesitate to come back and we’ll do some more specific tests.
« Last Edit: October 09, 2020, 06:02:35 PM by Weaver »
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spannerzone

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Re: Line fault fixed, now lots of errors and issues
« Reply #2 on: October 09, 2020, 11:03:43 AM »

Welcome to the forum, spannerzone.

If some websites consistently exhibit problems but not others then it’s nothing to do with your copper line or FTTC cab. You need to report this problem to your ISP. Are you using a wireless LAN ? If so then that could be the problem, so we need to rule that it first, so use an ethernet cable from your PC to your router and test various websites. If wireless does not seem to be the cause then report the problem to your ISP.

Don’t hesitate to come back and we’ll do some more specific tests.

Hi, all tests via ethernet, 4 different PCs in use.  I've just found my old BT modem and Plusnet router and hooked them up, I've never used them since first getting FTTC... however they work perfectly and all sites accessible...go back to my Draytek and issues are back. This is weird, both my Draytek 2762N were fully working before the line fault occurred! now they both behave the same but I guess the BT OR modem at least proves the line is good. I will now flatten the configs on the Drayteks and see if that resolves it.

Thanks for the reply  :D
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Black Sheep

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Re: Line fault fixed, now lots of errors and issues
« Reply #3 on: October 09, 2020, 11:46:52 AM »

Had a few issues with Drayteks over the years on small businesses, whereby the 3rd party maintainer would raise a fault stating 'multiple errors on line' (mainly the upstream).

But, once on-site the actual business occupants would comment they haven't noticed anything wrong, and subsequent tests with out HHT's always proved a great error-free circuit .... plug the Draytek back in, ring the 3rd party up and they still see errors .... rinse and repeat to no avail.

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spannerzone

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Re: Line fault fixed, now lots of errors and issues
« Reply #4 on: October 09, 2020, 12:11:18 PM »

Hi, thanks for that, slightly worrying... I am sure both my Drayteks are now faulty as a result of the line fault. I've reset them, built config from scratch, same results, loaded previously good config, same result, upgraded to latest firmware and reset, same result. Plug in OR modem and Plusnet router and all is good... back to Draytek's and both connect and sync as expected but some sites fail to load. I wouldn't have believed it if I hadn't seen it myself!

Now I'm going to try setup the OR modem and use with a Draytek seeing as it has all my network settings in it (mac binding etc)

What a pain in the arse this has been... all because an OR engineer crushed my twisted pair in the cabinet door/bracket and grounded them apparently and this somehow upset my kit. Just plain weird.

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spannerzone

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Re: Line fault fixed, now lots of errors and issues
« Reply #5 on: October 09, 2020, 02:03:59 PM »

Well just to conclude this little sage, the Openreach FTTC modem works perfectly with my Draytek 2762n via the ewan port, so for now that's the solution, I am still perplexed how 2 of these Drayteks failed to work after my line was repaired. I guess I'll try going through all the settings another day.
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spannerzone

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Re: Line fault fixed, now lots of errors and issues
« Reply #6 on: October 10, 2020, 12:01:05 PM »

Solved, :fingers:    the issue was my Draytek's MTU was set too high (1500) which may have happened when I factory reset the 2762N and failed to notice this setting had probably changed from 1492 (or maybe it was 1500 previously and worked?!)  and  Draytek said to lower it, 1492 works and websites all now available again. Since the line repair I find my download speed is down by about 4mbps and upload slightly better.

« Last Edit: October 10, 2020, 12:05:21 PM by spannerzone »
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Weaver

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Re: Line fault fixed, now lots of errors and issues
« Reply #7 on: October 10, 2020, 01:48:40 PM »

If you have a two-box set-up, router and separate modem, then most likely your MTU will need to be 1492 bytes or less. This is because there is additional overhead in the PPPoEoE protocol used by routers talking to modems and vice versa which adds 8 bytes to every message, so a 1500 byte long message becomes 1508 bytes. So a 1492 byte long message plus 8 bytes becomes 1500 bytes which is the longest message that can be handled by every network. Some good kit and good networks can handle 1508 byte messages but very many systems can’t. Modern BT networks with the right modems and the right routers will be fine, but your system - possibly the Draytek - is one that can’t. Messages longer than 1500 bytes are called ‘baby jumbo packets’ and this capability is something well worth looking out for when shopping for routers or modems.

I bought a 3G USB network interface ‘dongle’ device a while back and found to my annoyance that its MTU is a mere 1440 bytes; it can’t even handle 1500 bytes, never mind 1508, and an MTU of 1600 bytes would be useful in any such device.
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spannerzone

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Re: Line fault fixed, now lots of errors and issues
« Reply #8 on: October 12, 2020, 11:45:29 AM »

If you have a two-box set-up, router and separate modem, then most likely your MTU will need to be 1492 bytes or less. This is because there is additional overhead in the PPPoEoE protocol used by routers talking to modems and vice versa which adds 8 bytes to every message, so a 1500 byte long message becomes 1508 bytes. So a 1492 byte long message plus 8 bytes becomes 1500 bytes which is the longest message that can be handled by every network. Some good kit and good networks can handle 1508 byte messages but very many systems can’t. Modern BT networks with the right modems and the right routers will be fine, but your system - possibly the Draytek - is one that can’t. Messages longer than 1500 bytes are called ‘baby jumbo packets’ and this capability is something well worth looking out for when shopping for routers or modems.

I bought a 3G USB network interface ‘dongle’ device a while back and found to my annoyance that its MTU is a mere 1440 bytes; it can’t even handle 1500 bytes, never mind 1508, and an MTU of 1600 bytes would be useful in any such device.

Thanks for that detailed information, much appreciated. When I used the seperate openreach FTTC modem it all worked as the Draytek defaulted to 1492 but for some reason the inbuilt VDSL modem defaults to 1500 on the Draytek after you do a factory reset.
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Weaver

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Re: Line fault fixed, now lots of errors and issues (Resolved)
« Reply #9 on: October 12, 2020, 12:16:18 PM »

Isn’t the Vigor 130 1508 byte PPPoEoE MTU ? I read something to that effect in some system software release notes. See https://support.aa.net.uk/Router_-_Vigor_130 and https://www.draytek.co.uk/products/business/vigor-130
« Last Edit: October 12, 2020, 12:31:15 PM by Weaver »
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