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DD
@screenvision.com

DD

Anon

[Connectivity] Xbox Live MTU issue

Hi forum,

Hopefully you are able at the very least is to point me in the right direction with my issue. Back in July and previous months, my xbox live connection was working. In August, my cable promotion ended and i had to sign back up for another promotion. Around the same time, my xbox live connection stop working. Every time i tried to sign in, I would get "MTU Error". On my linksys router, my MTU is set at 1500 (As it has always been). I reach out to Microsoft, and did a couple of test with them, same error. I called Comcast and explain what was going on, their reply was (As long as the Internet is working, it's not our problem). I would have agreed with them, if not for having two Xboxes in my house (one wireless/ one Wired). They are both giving me the same MTU error, I also hook both of them one at a time directly into the cable modem. Same error MTU error, i also taken one of the xboxes with me to a friend's house and connected it to their network. I got right in, no errors. So I have narrow down the problem to Comcast and i cannot seem to find anyone to help me. Any ideas?
ExoticFish
join:2008-08-31
Zebulon, NC

ExoticFish

Member

Is this the issue you're having ?

»support.xbox.com/en-us/p ··· d=979104

pflog
Bueller? Bueller?
MVM
join:2001-09-01
El Dorado Hills, CA

pflog to DD

MVM

to DD
Let's see what effective MTU is getting out onto the network.

From a windows machine (if you have a Mac or other *nix, let me know and I'll give you the equivalent commands), open a command prompt (start -> run, etc) and run:

ping -f -n 2 -l 1472 www.google.com

If you see this message:

Packet needs to be fragmented but DF set.

Drop the 1472 by 4, try again, etc until you get a ping response like:

Reply from 10.80.24.244: bytes=1472 time=1ms TTL=59

Once you find the # that works, go up by 1 at a time until you find where it gets fragmented. For example, suppose you tried:

1472: fragmented
1468: fragmented
1464: OK
1465: fragmented

Then you know the largest packet size you can send is 1464 bytes. Now add the size of the overhead (28 bytes) and you get a final MTU of 1492.

Respond back with this effective MTU or if you have any questions about how to do this. There are probably also sites out there that will give you this info (even the tweak test here at DSLR does I think), but the above method is good to know IMHO anyway.

ArrayList
DevOps
Premium Member
join:2005-03-19
Mullica Hill, NJ

ArrayList

Premium Member

what would effect the MTU?

pflog
Bueller? Bueller?
MVM
join:2001-09-01
El Dorado Hills, CA

pflog

MVM

said by ArrayList:

what would effect the MTU?

Any hop along the route could be the culprit, usually it's a misconfiguration. But it can be done purposefully, too. For example, on DSL networks that use PPPoE, the MTU is 1492 (due to 8 bytes of overhead for PPPoE). So using an MTU of 1500 there would cause fragmentation and issues.

DD
@screenvision.com

DD to ExoticFish

Anon

to ExoticFish
Yes, that is my error...
DD

DD to pflog

Anon

to pflog
Thanks for the help, as soon as i tried 1472, the ping test went through. When i raise it to 1473, i hit the packet needs to be frag message. So should i change my Linksys MTU to 1472? Because you said once i get the number to add 28 to it and i will get my MTU. Once i add 28, i get 1500 which is the max and i will also get the fragment message...
ExoticFish
join:2008-08-31
Zebulon, NC

ExoticFish

Member

Set it to the highest number possible without XBox live giving you an error.

DD
@comcast.net

DD

Anon

Ok, once i rebooted my linksys router and my cable modem, i am unable to ping anything higher than 1340. Anything higher than that, i get the DF frag message. Very strange, i was able to ping up to 1472 before the reboot. Any other ideas guys or do you know who i can contact over at Comcast to help me with this issue. Thanks in advance

beachintech
There's sand in my tool bag
Premium Member
join:2008-01-06

beachintech

Premium Member

are you seeing that problem without the router too? After the reboot

DD
@screenvision.com

DD

Anon

Yes, I am.. The largest packet that i can push across is 1340, anything larger, i get the DF frag message. Do you think it could be my Linksys router? I've had it since 2008...

DocDrew
How can I help?
Premium Member
join:2009-01-28
SoCal
Ubee E31U2V1
Technicolor TC4400
Linksys EA6900

DocDrew

Premium Member

said by DD :

Yes, I am.. The largest packet that i can push across is 1340, anything larger, i get the DF frag message. Do you think it could be my Linksys router? I've had it since 2008...

Do you have any VPN software installed? What is the MTU on your network adapter set to?

What are the results of the tweaks test?
»/tweaks

beachintech
There's sand in my tool bag
Premium Member
join:2008-01-06

beachintech to DD

Premium Member

to DD
said by DD :

Yes, I am.. The largest packet that i can push across is 1340, anything larger, i get the DF frag message. Do you think it could be my Linksys router? I've had it since 2008...

if you are taking your router out and still seeing the problem, then no. What model modem do you have?
nikeherc
join:2004-09-30
Tucson, AZ

nikeherc to DD

Member

to DD
If you get an MTU error when hooked directly to the modem, then there is a provisioning error with the modem. Call tech support and ask to them to roll and push the modem. I bet the problem will go away.

EG
The wings of love
Premium Member
join:2006-11-18
Union, NJ

EG

Premium Member

said by nikeherc:

If you get an MTU error when hooked directly to the modem, then there is a provisioning error with the modem. Call tech support and ask to them to roll and push the modem. I bet the problem will go away.

Exactly how is this a "provisioning" issue ?? The CC system uses the standard ethernet value/parameter of 1500 for the MTU.

beachintech
There's sand in my tool bag
Premium Member
join:2008-01-06

beachintech

Premium Member

its prob not a provisioning issue but i have seen weirder problems solved by rolling a modem

EG
The wings of love
Premium Member
join:2006-11-18
Union, NJ

EG

Premium Member

When in doubt, roll and re-provision I guess..

dslcreature
Premium Member
join:2010-07-10
Seattle, WA

dslcreature to DD

Premium Member

to DD
To troubleshoot this use a path scanning tool to find the lowest link from your computer.

»www.iea-software.com/mtupath
»www.elifulkerson.com/pro ··· oute.php