Problems with Xbox Live host migration with two Xbox 360s on the same LAN

[froob]

I've recently moved from a router running Tomato firmware (tomatousb.org version) to an ALIX 2D13 running pfSense (2.0 release). It's been running without a hitch, except for dropped connections when running two Xbox 360s on Xbox Live in the same game.

I set up pfSense using the instructions on this forum, including turning on UPnP, setting a static DHCP lease for each Xbox 360 and turning on static ports. When using only one Xbox it works perfectly. When using two Xboxes it works almost perfectly (one will occasionally say it can't get a connection to Xbox Live, but restarting it solves this).

However, if the two Xboxes are playing in the same game on Xbox Live (in this case Halo) often when a host migration occurs one of the Xboxes will continue in the game, and the other will be dropped. On the dropped Xbox, the game says it is connecting to a new host, and then it appears as if all the other players have dropped out and the game ends. This probably happens in 1 game out of 10.

My previous router with Tomato firmware didn't have any problems with this situation.

I know this is a bit of an obscure problem, but does anyone have any idea what the issue could be here? Any comments appreciated.