GetIfTable function

Overview

The GetIfTable function retrieves a table that contains a list of network interfaces on the local computer. Each entry provides detailed information about an interface, such as its index, description, type, MTU, speed, and operational status.

This API is part of the IP Helper (IPHL) suite and is commonly used for network diagnostics, monitoring, and configuration tools.

Syntax

DWORD GetIfTable(
  PMIB_IFTABLE pIfTable,
  PULONG       pdwSize,
  BOOL         bOrder
);

Parameters

• pIfTable – A pointer to a MIB_IFTABLE structure that receives the interface table.
• pdwSize – On input, specifies the size of the buffer pointed to by pIfTable. On output, receives the required size if ERROR_INSUFFICIENT_BUFFER is returned.
• bOrder – If TRUE, the table is sorted by interface index. If FALSE, the order is unspecified.

Return value

• NO_ERROR – The function succeeded.
• Other error codes – See System Error Codes for details.

Example (C++)

#include <winsock2.h>
#include <iphlpapi.h>
#include <iostream>
#pragma comment(lib, "iphlpapi.lib")
#pragma comment(lib, "ws2_32.lib")

int main() {
    DWORD dwSize = 0;
    GetIfTable(nullptr, &dwSize, FALSE); // Get required buffer size

    std::vector<BYTE> buffer(dwSize);
    PMIB_IFTABLE pIfTable = reinterpret_cast<PMIB_IFTABLE>(buffer.data());

    if (GetIfTable(pIfTable, &dwSize, FALSE) == NO_ERROR) {
        std::cout << "Interface count: " << pIfTable->dwNumEntries << std::endl;
        for (DWORD i = 0; i < pIfTable->dwNumEntries; ++i) {
            MIB_IFROW &row = pIfTable->table[i];
            std::wcout << L"[" << row.dwIndex << L"] "
                       << row.wszName << L" - "
                       << ((row.dwOperStatus == MIB_IF_OPER_STATUS_OPERATIONAL) ? L"Up" : L"Down")
                       << std::endl;
        }
    } else {
        std::cerr << "GetIfTable failed." << std::endl;
    }
    return 0;
}

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Remarks

• The MIB_IFTABLE structure contains an array of MIB_IFROW entries. Each MIB_IFROW provides detailed information about a specific interface.
• When targeting Windows Vista or later, consider using GetIfTable2 for IPv6 support.
• Use GetIfEntry to query a single interface by index.
• Remember to call FreeMibTable if you allocate a table with AllocateAndGetIfTableFromStack.