[vox] Xbox Live firewall rules?

[Bill Broadley]

Anyone have a linux box acting as a firewall for an xbox360?

Can you share your firewall rules?

My config is comcast -> cable modem -> desktop eth1 -> desktop eth0 ->
switch -> xbox360.  Basically I'm using my desktop as a home router.

So my desktop has 2 ethernet interfaces:
eth0: 192.168.1.1
eth1: public IP from comcast

Xbox360 = 192.168.1.22

I found:
http://support.xbox.com/en-US/xbox-live/connecting/network-ports-used-xbox-live

And:
http://support.xbox.com/en-US/xbox-live/connecting/error-your-network-does-not-have-sufficient-mtu-setting-979104

One potential problem is that whenever I dhcp an IP from comcast my MTU
is set to 576.  Can I just run ifconfig eth1 mtu 1500?  Well I can
definitely set my MTU after getting an IP, not sure what a random
connection negotiates at though.

I've tried several likely looking rulesets, even run wireshark, but I
can't find any failed network connections that would convince the xbox
that things aren't working.

I suspect that I can get my linux box to be a completely transparent
firewall (even rewriting the hop count if need be), but I figured
someone else has probably managed this.