GetIpForwardTable2 function

The GetIpForwardTable2 function retrieves the IP route entries on the local computer.

Syntax

IPHLPAPI_DLL_LINKAGE _NETIOAPI_SUCCESS_ NETIOAPI_API GetIpForwardTable2(
  ADDRESS_FAMILY        Family,
  PMIB_IPFORWARD_TABLE2 *Table
);

Parameters

Family

The address family to retrieve.

Possible values for the address family are listed in the Winsock2.h header file. Note that the values for the AF_ address family and PF_ protocol family constants are identical (for example, AF_INET and PF_INET), so either constant can be used.

On the Windows SDK released for Windows Vista and later, the organization of header files has changed and possible values for this member are defined in the Ws2def.h header file. Note that the Ws2def.h header file is automatically included in Winsock2.h, and should never be used directly.

The values currently supported are AF_INET, AF_INET6, and AF_UNSPEC.

Value Meaning
AF_UNSPEC
0
The address family is unspecified. When this parameter is specified, this function returns the IP routing table containing both IPv4 and IPv6 entries.
AF_INET
2
The Internet Protocol version 4 (IPv4) address family. When this parameter is specified, this function returns the IP routing table containing only IPv4 entries.
AF_INET6
23
The Internet Protocol version 6 (IPv6) address family. When this parameter is specified, this function returns the IP routing table containing only IPv6 entries.

Table

A pointer to a MIB_IPFORWARD_TABLE2 structure that contains a table of IP route entries on the local computer.

Return Value

If the function succeeds, the return value is NO_ERROR.

If the function fails, the return value is one of the following error codes.

Return code Description
ERROR_INVALID_PARAMETER
An invalid parameter was passed to the function. This error is returned if a NULL pointer is passed in the Table parameter or the Family parameter was not specified as AF_INET, AF_INET6, or AF_UNSPEC.
ERROR_NOT_ENOUGH_MEMORY
Insufficient memory resources are available to complete the operation.
ERROR_NOT_FOUND
No IP route entries as specified in the Family parameter were found.
ERROR_NOT_SUPPORTED
The request is not supported. This error is returned if no IPv4 stack is on the local computer and AF_INET was specified in the Family parameter. This error is also returned if no IPv6 stack is on the local computer and AF_INET6 was specified in the Family parameter. This error is also returned on versions of Windows where this function is not supported.
Other
Use FormatMessage to obtain the message string for the returned error.

Remarks

The GetIpForwardTable2 function is defined on Windows Vista and later.

The
GetIpForwardTable2 function enumerates the IP route entries on a local system and returns this information in a MIB_IPFORWARD_TABLE2 structure.

The IP route entries are returned in a MIB_IPFORWARD_TABLE2 structure in the buffer pointed to by the Table parameter. The MIB_IPFORWARD_TABLE2 structure contains an IP route entry count and an array of MIB_IPFORWARD_ROW2 structures for each IP route entry. When these returned structures are no longer required, free the memory by calling the FreeMibTable.

The Family parameter must be initialized to either AF_INET, AF_INET6, or AF_UNSPEC.

Note that the returned MIB_IPFORWARD_TABLE2 structure pointed to by the Table parameter may contain padding for alignment between the NumEntries member and the first MIB_IPFORWARD_ROW2 array entry in the Table member of the MIB_IPFORWARD_TABLE2 structure. Padding for alignment may also be present between the MIB_IPFORWARD_ROW2 array entries. Any access to a MIB_IPFORWARD_ROW2 array entry should assume padding may exist.

Requirements

   
Minimum supported client Windows Vista [desktop apps only]
Minimum supported server Windows Server 2008 [desktop apps only]
Target Platform Windows
Header netioapi.h (include Iphlpapi.h)
Library Iphlpapi.lib
DLL Iphlpapi.dll

See Also

CreateIpForwardEntry2

DeleteIpForwardEntry2

FreeMibTable

GetBestRoute2

GetIpForwardEntry2

InitializeIpForwardEntry

MIB_IPFORWARD_ROW2

MIB_IPFORWARD_TABLE2

NotifyRouteChange2

SetIpForwardEntry2