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MTU size problems when switching router from fibre to DSL

petecook
Newbie
Posts: 2
Registered: 12-10-2016

MTU size problems when switching router from fibre to DSL

After our recent move, we've gone from fibre to DSL but I received no starter pack and no new router, so I've switched our existing plusnet fibre router (2704n) over to DSL mode. This works but the MTU size is causing major packet loss for devices that cannot manually change the MTU size. I can change it on laptops (from 1500 to 1458..) and things work correctly but this is not possible on iOS phones and some other devices. I also cannot see where to change the MTU size on the router anywhere in the advanced settings.

Basically it seems like I need a new DSL router from Plusnet that is compatible with my DSL connection, or I need to somehow change the MTU size setting on my 2704n router. Any thoughts?

5 REPLIES
LennyNero
Hooked
Posts: 6
Registered: 30-10-2015

Re: MTU size problems when switching router from fibre to DSL

I dont think you need to change the MTU size (if that MTU is max transmission unit). 1500 is pretty much a standard most stick to now-a-days ...not getting into the ethernet vs pppoe and other things, overhead and the like. You dont seem to say what the problem is, what is it doing, or not ?
Community Veteran
Posts: 4,916
Thanks: 335
Fixes: 16
Registered: 10-06-2010

Re: MTU size problems when switching router from fibre to DSL

There is/was a firmware bug with the 2704n when it is switched to ADSL mode. I think there was a remote fix that Plusnet did individually for the affected people, I'm not sure it's possible to fix it yourself.

Community Gaffer
Community Gaffer
Posts: 12,853
Thanks: 675
Fixes: 65
Registered: 04-04-2007

Re: MTU size problems when switching router from fibre to DSL

This is a known issue.

Solutions include:

  1. We can push the MTU manually from here (not persistent so won't survive a factory reset)
  2. Firmware update. The issue was specific to older firmware revisions, so a remote firmware update might help (and it would be persistent)
  3. We send a unit that has the ADSL firmware installed

I don't have access to the ACS at the moment, so the quicker option is probably 3. If I despatch a device to the address associated with your account would that suit?

Bob Pullen
Plusnet Products Team
If I've been helpful then please give thanks ⤵

petecook
Newbie
Posts: 2
Registered: 12-10-2016

Re: MTU size problems when switching router from fibre to DSL

@bobpullen That would be great.

Community Gaffer
Community Gaffer
Posts: 12,853
Thanks: 675
Fixes: 65
Registered: 04-04-2007

Re: MTU size problems when switching router from fibre to DSL

Sorted. Should turn up in a day or two Smiley

Bob Pullen
Plusnet Products Team
If I've been helpful then please give thanks ⤵