uses
WinSock;

Function sendarp(ipaddr:ulong;
temp:dword;
ulmacaddr:pointer;
ulmacaddrleng:pointer) : DWord; StdCall; External 'Iphlpapi.dll' Name 'SendARP';

procedure TForm1.Button1Click(Sender: TObject);
var
myip:ulong;
mymac:array[0..5] of byte;
mymaclength:ulong;
r:integer;
begin
myip:=inet_addr(PChar('192.168.6.180'));
mymaclength:=length(mymac);
r:=sendarp(myip,0,@mymac,@mymaclength);
label1.caption:='errorcode:'+inttostr(r);
label2.caption:=format('%2.2x:%2.2x:%2.2x:%2.2x:%2.2x:%2.2x',[mymac[0],mymac[1],mymac[2],mymac[3],mymac[4],mymac[5]]);
end;

（出处：DelphiFans.com）