STL map or hash map using struct as data and find it

Hi,

I'm trying to learn some STL using map or hash_map would maybe even
better to use but I don't really know how to find a specific struct
depending on a DWORD value that is in range of two DWORD values (see
below for more).

So what I trying to achieve is creating a look up table of a IP adress
with a start adress (a DWORD value) and a end adress (a DWORD
value) which I would like to look up to the get the Country name
using a specific IP adress (also in DWORD) which is random access to
the table.

It is easy to use vector, linked list but I would like to try to use
map or hash map for more effecient way to look up or at least test it
out to compare some.

The code is basicly looks like this:

//Struct definition
struct IPCOUNTRY
{
    DWORD startIP; //IP start adress in DWORD which is always unique
    DWORD endIP; //IP end adress in DWORD which is always unique
    char COUNTRYNAME[45]; //Country name like England, Germany Spain
etc...
};

typedef map <DWORD, IPCOUNTRY> mIPC;
mIPC mIPcountry;

//Initilize the map when and call this function during start up
void initilizeMap()
{

               //read data from file and insert it into a map
    IPCOUNTRY g_structIP;
    FILE *fp=NULL;
    fp=fopen("ipcountry.dat", "rb");

    if(fp!=NULL)
    {
        while( !feof( fp ) )
        {
            if(fread(&g_structIP, sizeof(g_structIP), 1, fp)!=0)
            {

                      mIPcountry[g_structIP.startIP] = g_structIP;
            }
        }
    }
    fclose(fp);
}

struct compareIPC
{
  bool operator()(const IPCOUNTRY* ipc1, const IPCOUNTRY* icp2) const
  {

    return strcmp(ipc1, ipc2) < 0;
  }
};

//This function will be called with IPaddress set and set the
countryname depending which country it belongs
//to using the map look up table
int lookupCountryName(DWORD IPadress, char *countryname)
{
   //ok here I'm lost what I should exactly do

   mIPC::iterator mIPCbegin = mIPcountry.begin();
   mIPC::iterator mIPCend = mIPcountry.end();

   return 0;
}