#define ETH_FRM_SIZE 1500

void main(void) {
   
   BYTE EthFrmBuf[ETH_FRM_SIZE];
   BYTE broadcast_IP[4] = {255,255,255,255};
   BYTE zero_ip[4] = {0, 0, 0, 0};
   BYTE ip_addrr[4];
   ...
}