Hi All, I posted this question several days before, as if no one reply, any help, hint would be highly appreciated! PLEASE SAVE ME! Now I am having trouble in Ethernet bridge and 802.1Q VLAN, I have the following network: Internet | | Gateway | | <--------- If insert one Ethernet bridge box in here ,somethings changes | H u b ( one normal hub or switch , no VLAN settings) | \ | \ D-Link 802.1Q VLAN Switches (their uplink port-port 1 connected to the upper hub are tagged, those ports connected with PCs are untagged). Our client PCs connect to these VLAN Switches, they access Internet through that UPNP gateway, It works all OK; Every PC connects to one untagged port in a 802.1Q VLAN Switch , this untagged port and the tagged uplink port (e.g. port 1) make up of one VLAN, the tagged port 1 is a common uplink port , So from the gateway we can see these VLAN ID of PCs, so far it all work fine; but when I insert one Ethernet bridge box ( one linux box, kernel 2.4.26, ebtables-brnf-6_vs_2.4.26 patch, one rt8139 NIC, one e100 NIC) between the gateway and the Hub, somethings changed: I was not able to log in hotmail, maybe also on certain websites. For example, I access www.hotmail.com <http://www.hotmail.com/> , it loads OK. When I input my account, and hit Login, it goes to a error page(DNS error or server not found) after a moment. Except the above site, maybe also have others, but most sites work fine, very strange! I am sure that this Linux Ethernet bridge is only transparent bridge, no any Iptables filter and rule. If I remove the tag for VLAN(just change the port 1 to untagged), also with this Linux Ethernet bridge it works all OK, also have no hotmail login error. Very strange, it as if the issue is on VLAN , tag, or Linux Ethernet bridge , I have no idea of it now! Is it a MTU issue on Bridge? I am stuck here now! Any help, comments, hints would be greatly appreciated! If you need more info on it, please let me know soon! Thanks! Kingz