xbox failing mtu test at linux router

rbees · 11-01-2008, 09:47 PM

Ladies & Gentlemen

I have been trying to get my son's xbox 360 to have internet access through my Debian Testing (Lenny) router and a cable modem. So far we have not been able to get the xbox to pass the mtu test. I have set the mtu in the /etc/network/interfaces file for both nic's in the linux box.

I have tried setting port forwarding in my firewall (Firestarter) and opening the ports that xbox needs but so far have not had success. I may not be setting and opening the ports correctly as this is my first experience with opening holes in my firewall.

So far a google search has not revealed a way to test the mtu of my router but I am still looking.

Thanks in advance.

rbees · 11-02-2008, 06:26 AM

OK

I found tracepath which tells me that although my linux router is starting with an mtu of 1500 when it gets a little way through the proccess it drops to 576. It is also failing at the second hop? I think

Code:

~$ tracepath 207.44.232.90
 1:  .local (192.168.x.x)                            0.383ms pmtu 1500
 1:  192.168.x.x (192.168.x.x)                              1.590ms
 1:  192.168.x.x (192.168.x.x)                              1.428ms
 2:  192.168.x.x (192.168.x.x)                              2.502ms pmtu 576
 2:  no reply
 3:  x.19.48.62 (x.19.48.62)                            8.756ms
 4:  static.unknown.charter.com (96.34.32.66)               7.869ms
 5:  static.unknown.charter.com (96.34.32.42)              12.831ms
 6:  static.unknown.charter.com (96.34.32.45)              12.369ms
 7:  64.127.129.9 (64.127.129.9)                           18.222ms
 8:  eqix.chcg.twtelecom.net (206.223.119.36)              22.857ms asymm 13
 9:  hagg-03-ge-0-0-0-540.hsto.twtelecom.net (66.192.246.206)  51.767ms asymm 16
10:  et3-3.ibr01.hstntx1.theplanet.com (70.87.253.153)     49.397ms asymm 18
11:  po1.car05.hstntx1.theplanet.com (207.218.223.18)      50.410ms asymm 19
12:  no reply
13:  no reply
and so on

A little more digging shows that eth1 is not set to a large enough mth for the xbox which requires an mtu of 1365.

In my /etc/network/interfaces I have in set like so

Code:

allow-hotplug eth1
auto eth1
iface eth1 inet dhcp
pre-up /sbin/ifconfig $IFACE mtu 1365

I have also tried to hard set it with mtu 1365 with no success either.

OK, so I ran /sbin/ifconfig eth1 mtu 1500 and now tracepath reports the mtu as 1500 as all the way through. Now when the boy gets up he can try his xbox again. If it works he will be able to talk to his girlfriend again. He has been having withdrawl spymptoms since He moved back home where his cell phone dosen't work well enough to spend three hours a day on the phone with her. Ah, young love, we have all been there.

Success.

Thanks for all the help ya-all gave me