Hi All, I have noticed some odd behaviour on both Vista and Windows 7 when installed on a dual-homed machine. My machine has the following network configuration: Interface 1: 10.10.0.2/24, default route via 10.10.0.1 Interface 2: 192.168.0.115/16, no default route. The network connected to interface 2 is a large ethernet with some 4000 connected devices. Traffic on this network is mostly PPPoE although IPv4 is used for management and diagnostics. Many devices connected to this network are between 10-50ms away (measured using a ping with 1k payload). Iif I want to "ping" something on the /16 network a single ARP request is sent to this network's broadcast address. So far so good. It seems that if the ARP request does not receive a response in a certain, arbitrary amount of time then something odd happens. An entry for the destination IP address is created in the system's ARP table - bound to the MAC address of the default router on the other network interface. Traffic destined for the 192.168.x.x address is now sent out of the wrong interface, through the router and out towards the Internet. Removing the rogue entry in the ARP table will often cure the problem (a correct ARP entry is then created) for a minute or two. After that, the rogue ARP entry comes back and traffic is once again routed over the wrong interface. Surely this is the incorrect behaviour. Any thoughts? I am happy to provide further debugging output on request. Regards, Charlie

Hi Charlie, Based on my research, I would like to share the following with you: Source IP address selection on a Multi-Homed Windows Computer Default Gateway Configuration for Multihomed Computers Hope this helps. Thanks.Nicholas Li - MSFT