Posts Tagged ‘Zyxel’

* Mixed WPA/WPA2 mode on ZyXEL Prestige 660HW-T1

Posted on June 28th, 2009 by whinger. Filed under Tech.

Problem: Broadcom wifi adaptor in HP 6735s running Vista won’t connect to internet via Zyxel Prestige 660HW-T1 running WPA mixed mode

Issue: WPA1 support on Vista with the Broadcom drivers doesn’t seem to work, but turning on Mixed Mode WPA2/WPA1 on the Zyxel stops internet access; meanwhile we have some WPA1-only devices (Belkin print server) so we can’t use WPA2-only

Solution: updating the Broadcom drivers didn’t help, and neither did getting the latest firmware for the Zyxel. Eventually I realised that some sites (mainly google) worked while others didn’t and (after a few tests) figured out that the MTU size needed to be lowered to 1482.

Whinge: Why on earth would WPA mixed mode alter the maximum MTU? That’s just crazy.

FWIW, changing the MTU on the Zyxel is a fairly complicated thing: this page describes how to do it temporarily and permanently. I’d also recommend changing the MTU on Windows because otherwise the router will have to split up your traffic into chunks, and you can actually get away with just changing the Windows MTU if you don’t want to change router settings; download the excellent TCPOptimizer from and set the MTU with that.

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