CreateIPForwardEntry() returning ERROR_INVALID_PARAMETER... please help!!

[b_girl]

Hello, I am currently needing to use CreateIPForwardEntry() to add an entry into the routing table. I have created a PMIB_IPFORWARDROW structure and I know that I've assigned something incorrectly but am not sure what it is. Can someone please take a look at this to see if you notice anything incorrect? I have a feeling it might be dwForwardMask - which I want to be 255.255.0.0 Thanks.. [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)] public struct PMIB_IPFORWARDROW { public UInt32 dwForwardDest; public UInt32 dwForwardMask; public UInt32 dwForwardPolicy; public UInt32 dwForwardNextHop; public UInt32 dwForwardIfIndex; public UInt32 dwForwardType; public UInt32 dwForwardProto; public UInt32 dwForwardAge; public UInt32 dwForwardNextHopAS; public UInt32 dwForwardMetric1; public UInt32 dwForwardMetric2; public UInt32 dwForwardMetric3; public UInt32 dwForwardMetric4; public UInt32 dwForwardMetric5; } ... UInt32 uintO1, uintO2, uintO3, uintO4, dwForwardDest, dwForwardNextHop; uintO1 = Convert.ToUInt32("10"); uintO2 = Convert.ToUInt32("30"); uintO3 = Convert.ToUInt32("0"); uintO4 = Convert.ToUInt32("0"); dwForwardDest = (uintO1 << 24) + (uintO2 << 16) + (uintO3 << 8) + uintO4; uintO3 = Convert.ToUInt32("79"); uintO4 = Convert.ToUInt32("5"); dwForwardNextHop = (uintO1 << 24) + (uintO2 << 16) + (uintO3 << 8) + uintO4; PMIB_IPFORWARDROW pmibip = new PMIB_IPFORWARDROW(); pmibip.dwForwardDest = dwForwardDest; unchecked { pmibip.dwForwardMask = (UInt32)((255 << 24) + (255 << 16) + (0 << 8) + 0); //pmibip.dwForwardMask = 24; //pmibip.dwForwardMask = (uint)0x00255255; } pmibip.dwForwardPolicy = Convert.ToUInt32("0"); pmibip.dwForwardIfIndex = dwForwardNextHop; //index of adaptor when doing route print displays as being same as gateway pmibip.dwForwardNextHop = dwForwardNextHop; pmibip.dwForwardType = 4; pmibip.dwForwardProto = PROTO_IP_NETMGMT; pmibip.dwForwardAge = 43200; //12 hours