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MTU setting ?

waynem
Grafter
Posts: 133
Registered: 03-07-2012

MTU setting ?

Hi ..
what should this be ? am using belkin N150  ... on my old belkin  it was  something 1430  .. but new belkin shows 1500    .... just wondered if this needed to be adjusted
thanks
8 REPLIES
Superuser
Superuser
Posts: 9,378
Thanks: 692
Fixes: 51
Registered: 06-04-2007

Re: MTU setting ?

An MTU setting of 1500 is the normal Windows default. There is no need to change it in normal circumstances.
David
waynem
Grafter
Posts: 133
Registered: 03-07-2012

Re: MTU setting ?

Hi
thanks for that  , it seems everytime my connection is reset  by BT/PN  eg IP profile  i get a MTU fault on XBOX live  and 100% packet loss , i tend to have to restart my router again to get my mtu back !
any ideas ?
cheers
Superuser
Superuser
Posts: 9,378
Thanks: 692
Fixes: 51
Registered: 06-04-2007

Re: MTU setting ?

Is the UPnP setting different on your old router and new one? Perhaps the gaming community are better placed to help with this problem,
David
waynem
Grafter
Posts: 133
Registered: 03-07-2012

Re: MTU setting ?

UPnP setting is the same as old router i think ...
trouble is , when i reset the router to get MTU back ... BTW  sees it as a disconection and then we head into a downward trend again ..
on my router if i log in and look at setting it shows 1500  .... but the text underneath says "Do not make changes to the MTU setting unless your ISP specifically requires a different setting than 1454"  ...so am right in thinking that it should be set 1454 Huh
cheers
Superuser
Superuser
Posts: 9,378
Thanks: 692
Fixes: 51
Registered: 06-04-2007

Re: MTU setting ?

In my opinion it should be set to 1500 unless problems are encountered with some graphics rich websites. I think such problems are probably hardware dependent especially with regard to graphics cards. In this case 1400 usually works.
I believe 1454 is the theoretical optimum for PPPoE over ATM to ensure there is no wasted space in an ATM cell if all transmitted TCP packets are maximum length. The calculated benefit from this is a boost in download speed of around 90kbps. We use PPPoA which has diiferent overheads. Amidst the vagaries of the Internet is 90kbps worth bothering about?
David
Community Veteran
Posts: 6,313
Thanks: 86
Fixes: 3
Registered: 08-01-2008

Re: MTU setting ?

Absolutely correct spraxyt - an explanation here: http://www.mynetwatchman.com/kb/adsl/pppoemtu.htm
Not all routers report the 'true MTU' though and 1500 could be the 'correct' setting if that's already allowing for some of the overhead (sometimes reported this way to simplify things and reduce confusion but all too often has the opposite effect).
If you gradually reduce the setting until things work then you  might find the 'optimum setting' but this would likely involve many rooter reboots which you are absolutely aware is not a good thing, given the small difference between 'optimal' and 'nearly optimal' I'd definitely recommend following the advice in the previous post and try 1400 at least to see if that solves the packet loss issue.
Call me 'w23'
At any given moment in the universe many things happen. Coincidence is a matter of how close these events are in space, time and relationship.
Opinions expressed in forum posts are those of the poster, others may have different views.
waynem
Grafter
Posts: 133
Registered: 03-07-2012

Re: MTU setting ?

Thanks guys , although it sounds way to technical for me ! .. i raised a ticket and the reply seems to say that it could be a faulty router ... my previous router did have a different MTU setting and i never ever had this kind of problem , would there be any detriment to setting it at 1454 ?
cheers guys
Community Veteran
Posts: 6,313
Thanks: 86
Fixes: 3
Registered: 08-01-2008

Re: MTU setting ?

Shouldn't be much (if any) detriment other than the inevitable rooter reboot when changing such settings.
Call me 'w23'
At any given moment in the universe many things happen. Coincidence is a matter of how close these events are in space, time and relationship.
Opinions expressed in forum posts are those of the poster, others may have different views.