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MTU help please

RichardDNorth
Dabbler
Posts: 18
Registered: 13-04-2013

MTU help please

I would be very grateful for help with my MTU number. My connection often drops to a crawl, and the fix - temporary - is to switch from 1454 to 1410, or vice versa. Each time, the fix lasts for a week or two.
I am using a Belkin Share router and have often had and followed phone support advice to restore factory settings. One adviser said to try 1410 rather than the default 1454.
The router's settings include PPPoA, VC MUX, and IP assigned by ISP.
Any help would be much appreciated.
36 REPLIES
Community Veteran
Posts: 5,472
Thanks: 292
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Registered: 11-08-2007

Re: MTU help please

Without going into too much detail at this stage, I generally get the best results with 1430 or 1458.
The numbers you quote are not typical for UK PPPoA connections  Undecided
When you change the MTU value, does your router restart the internet connection ?
It is unlikely that a wrong MTU would cause the problem you are describing !
Community Veteran
Posts: 38,460
Thanks: 1,027
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Registered: 15-06-2007

Re: MTU help please

A few questions
What operating system are you using and are the speeds wired or wireless
Can you post the router stats - noise margin, speeds and attenuation
Community Veteran
Posts: 19,101
Thanks: 443
Fixes: 21
Registered: 31-08-2007

Re: MTU help please

You could be on the right tack there Jim, I suspect that it's the modem/router restart and hence resync that giving an improvement for a while.
RichardDNorth
Dabbler
Posts: 18
Registered: 13-04-2013

Re: MTU help please

Thank you, Jim.
In the morning I'll open up the router's settings and aim to get those numbers.
RDN
RichardDNorth
Dabbler
Posts: 18
Registered: 13-04-2013

Re: MTU help please

Thank you for your invitation for more information...
I hope this attachment from my Belkin Share is helpful.
RichardDNorth
Dabbler
Posts: 18
Registered: 13-04-2013

Re: MTU help please

Here are what I hope are the relevant Belkin Share settings.
My Belkin software is loaded on a Win 7 64 bit PC; many machines connect wireless to the Belkin, and Sky by Ethernet.
Community Veteran
Posts: 19,101
Thanks: 443
Fixes: 21
Registered: 31-08-2007

Re: MTU help please

Hmm, your sync speed (Downstream Data Rate) should be a lot higher with that attenuation, your exchange must be quite close.
You either have a lot of noise on the line, or things plugged in without a filter, or poor quality or faulty filters, unless your Belkin is going faulty.
Can you hear/have you heard any crackling or other noises on the line when using the phone? Have you had any problems with incoming or outgoing calls?
Do you have a Master Socket like the one on the left? And do you have any extension phone sockets, and where are you currently plugged in?
Do all your Microfilters look like this? and is everything that's plugged into the line connected via a filter?
If you can provide that information and also tell us how old the Belkin is?
RichardDNorth
Dabbler
Posts: 18
Registered: 13-04-2013

Re: MTU help please

Thank you Anotherone.
(1)
Before I opened this thread I find I had submitted a ticket to PlusNet (my connection being wonky, I thought I had failed to do so....). Their person has texted to say they are hoping to stabilise the line with interleaving and will get back to me...
I say that in hopes of avoiding crossed-wires (as it were).
(2)
Following yr inquiry for information:
You suggest that my filters or the Belkin may be failing....
I have several BT phone wall sockets which look more or less like the middle LJU one pictured in yr reference link. I do have a Mastersocket. In the attic there is also an ancient lozenge-shaped junction box.  (I recently carefully disconnected one of the extension phone sockets from the attic junction box.) All the phone sockets in the house are working, including the Mastersocket hidden socket) and there is no noise on the line. Every phone is connected to the wall sockets via microfilters. Sky On Demand works fine when the broadband is working well. The Belkin Share router has firmware updated from Summer 2010, and that may be its age.
I hope that is useful information....
Community Veteran
Posts: 19,101
Thanks: 443
Fixes: 21
Registered: 31-08-2007

Re: MTU help please

The ticket response is a standard response and I doubt will help your situation in view of the way you have described what is happening.
Is the Sky plugged into the line as well and is it plugged in via a filter?
As you have a junction box in the attic, does the BT incoming cable go to this box? I'm guessing it may be an overhead line.
How many other cables leave this junction box? Can you tell me the colour of the wires both for the incoming BT line and any going to sockets?
RichardDNorth
Dabbler
Posts: 18
Registered: 13-04-2013

Re: MTU help please

Thanks for that ... I'll get checking - yes, it's an overhead telephone cable from the street.
Community Veteran
Posts: 19,101
Thanks: 443
Fixes: 21
Registered: 31-08-2007

Re: MTU help please

Oh, in the meantime if you get one of your "connection drops to a crawl" situations, straight away grab a copy of the Belkin stats and post them when you can.
RichardDNorth
Dabbler
Posts: 18
Registered: 13-04-2013

Re: MTU help please

Thanks so much for this.
I have just cured a slow afternoon (by switching MUT numbers, or maybe by some other thing which happens when I switch) - but I will post slow-session numbers as soon as I have them.
Here is a snap of the junction box in the attic.
Four colours are attached to all terminals, but a white one is additionally attached to the one which goes to the router's socket.
Community Veteran
Posts: 19,101
Thanks: 443
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Registered: 31-08-2007

Re: MTU help please

Is any of those wires the BT incoming cable? The colours don't tie up with conventional BT incoming cable. Does the BT cable go direct to the Master socket perhaps? Can you post the exact model number of your Belkin Share? What Operating System are you using?
I'm suspecting that your issues are more related to wiring, but we won't jump to any conclusions yet.
RichardDNorth
Dabbler
Posts: 18
Registered: 13-04-2013

Re: MTU help please

Earlier this morning, I had a "slow" patch and took a snap of the numbers at 0750. Then I restarted the Belkin (not the MTU switchover) and got back up to speed - then retook the snap of numbers at 1755. (Snaps attached.)
I think the overhead external GPO line comes into the Mastersocket and continues up to the attic junction box and thence on to what must be another splitter/junction box for the two remaining sockets.
The Belkin Share is an F7D3402v1, which was I think released, made and bought in 2010.
The Belkin software is loaded on a Win 7 PC 64-bit. (Is that what you were asking?)
It occurs to me look at the colours of the incoming GPO cable - I'll do that now and get back to you.