Can't use Xbox Live on Three 4G broadband - MTU Size Issue?

Hi,

Please excuse this post from a newbie, in particular if it's already been answered before.

I've used a Three 4G connection for a few months and it works reasonably well. One persistent issue is that my son can't seem to play multi-player games on his Xbox. It works ok with an O2 SIM in the Router, but not Three.

I wonder whether it may be down to the MTU size - the minimum specified by Xbox is 1384 whereas my router (TP-Link TL-MR6400) is stating it's set at 1358. I've spoken to both tp-link and Three and have been told that there's no way to change it as it's set by Three.

Does anyone have any ideas as to how to get around this issue, or indeed whether the MTU size is actually the likely cause of the problem?

Many thanks,

Neil

My Three router has MTU 1500 and MSS 1460. Not set by myself.

Have you confirmed by diagnostics what the actual MTU is though to an end point? It is possible the MTU is being downsized by Three as all the router is setting is the maximum MTU, it can't control what happens downstream from it.

EDIT : This page shows how to confirm MTU.

Edited by ian72 (Mon 16-Aug-21 10:49:53)

Hi Ian72 / everyone,

Thanks for the quick response.

Going through the MTU sizing page, it gives the answer for the max packet size as 1330 - with the 28 byte header, this equates to 1358 which is the same as the router info page is displaying as the MTU size.

Does this point to any way around the issue?

Many thanks,

Neil

Same here . (For the pings).
Thanks Ian for the suggestion.

Also I just checked my Win 10 setting, which is 1500. (Command prompt >> netsh interface ipv4 show subinterfaces)

Edited by pluralist (Mon 16-Aug-21 14:22:34)

It is unlikely to be the MTU, it is more likely the game server can't connect inbound to you. This is because of something called 'CGNAT'.

If you can control the APN your router is using try "3internet" if you are using "three.co.uk" and see if that makes any difference.

Sorry - my ignorance coming out again.

When you say "try 3internet", what are you referring to pls? I'm currently using a profile called Three(default: 1) with APN of "three.co.uk" - username / pwd are both blank.

Are you suggesting changing the APN to the text "3internet"?

Thanks,

Neil

PS If this is of any interest or help, on the internet config page, Mobile Data is on, Roaming is off, NAT is on, authentication type is CHAP.

Yes, try changing the APN from three.co.uk to 3internet

I'm not sure how the tp-link routers work when changing the APN but in my case i have the option to add an APN. All i need to fill in is the APN and the name of said APN, the name can be anything in my case but the APN must be 3internet or three.co.uk
On my router, this is what's listed.

Profile name: Anything
Set as Default Profile: Yes
User name: Leave Blank
Password: Leave Blank
APN: 3internet or three.co.uk

Then i click save, Hopefully the 3internet APN will fair better for you as it does with me in regards to gaming.

In reply to a post by neilmw:

Are you suggesting changing the APN to the text "3internet"?

Yes, exactly that. As woodmass has posted, it depends on your router/modem how you actually do the change.

It might solve the problem, but you may get slower speeds for some reason (my PAYG voice SIM speeds slow down!).