Knowing with Network Interface will be used
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Hi all, I am writing a system where a client communicates with a server and amongst other things tells the server what the client's IP and subnet mask are. However, when there are more than 1 network cards on a PC, how can I programmaticaly know which interface a packet is going to be sent on (for a particular destination)? I know how to get a list of interfaces and relevant details but don't know which one to use. Mark
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Hi all, I am writing a system where a client communicates with a server and amongst other things tells the server what the client's IP and subnet mask are. However, when there are more than 1 network cards on a PC, how can I programmaticaly know which interface a packet is going to be sent on (for a particular destination)? I know how to get a list of interfaces and relevant details but don't know which one to use. Mark
mmica wrote: I know how to get a list of interfaces and relevant details but don't know which one to use. The routing service on the PC will determine from the destination address which interface to use. If, for some reason, you need to select an interface in your app, though, the information stored in the routing table for the PC should be sufficient. Knowing the destination IP address and subnet mask, you should be able to compare it to the routing table in the machine to find which interface the address fits. If you AND the IP address of the host you want to reach with the subnet mask, the resulting network address should fit into one of the route specifications in the routing table. The illustrations here - The IP Routing Table - MSDN[^] - provide examples and an excellent explanation of how they're used. Will Build Nuclear Missile For Food - No Target Too Small