Hello monks, I am trying to write a function that, given an array of IP addresses, will run ARP requests to find out which IPs are currently assigned to live hosts. I am in need of some pointing in the right direction for propper tools/modules to use. I tried Net::ARP however it primarily reads the ARP cache which does not provide up-to-date information. also it's packet construction requires a target MAC address. If I had the MAC address I wouldn't need to send the request ;). What I actually need is to create broadcast packets of "Who has <ip address>" and then listen for the replies. I think Net::Pcap is probably half of what I need. If someone can point me to a good way to do the requests, and/or tell me if Net::Pcap is really what I should be messing with here, I'd appreciate it. Cheers!

UPDATE: Well as per my other post at Net::Pcap garbage Output Pcap has not worked out well for me so far. I think I am going to try approaching this from a different angle in my obvious lack of full understanding of Pcap. I'm going to try using Net::Frame::Dump to tackle this problem instead.

Update #2: : It would appear that the garbage output I was getting was from the NetPacket decode functions and I was mistakingly attributing them to Pcap due to the decimal converted values it was giving me in the lookup command. I switched over to using Net::Frame::Dump::Online and Net::Frame::Simple. After some leg work I have gotten this to work. code attached if anyone cares to comment 

#!/usr/bin/perl

use Net::ARP;
use Net::Netmask;
use Net::Frame::Simple;
use Net::Frame::Dump::Online;


my $dev= "eth1";
$interface= shift;
 $ifconf= `ifconfig $dev`;
$ifconf=~ /\d+\.\d+\.\d+\.\d+/;
 $ipdec= $&;
 $ifconf=~ /Mask:\d+\.\d+\.\d+\.\d+/;
 $nmaskdec= $&;
 $nmaskdec=~s/Mask://;

my $netblock= $ipdec . ":" . $nmaskdec ;
$netmask=new Net::Netmask ($netblock);
my @iprange = $netmask->enumerate;


$arpDump=Net::Frame::Dump::Online->new(
   dev    => $dev,
   filter => 'arp');

$arpDump->start;

my %livehosts;
my $reply;
$counter=0;
while ($counter<3){
    for $ipts (@iprange){
        Net::ARP::send_packet($dev,$ipdec,$ipts,"00:18:de:34:8e:7b","f
+f:ff:ff:ff:ff:ff","request");
    }
    until ($arpDump->timeout){
        
        if ($next=$arpDump->next){
            my $r=Net::Frame::Simple->newFromDump($next);
            $opc=$r->ref->{ARP}->opCode;
            next unless $opc == 2;
            $livehosts{$r->ref->{ARP}->srcIp}=$r->ref->{ARP}->src;
        }
    }
    $arpDump->timeoutReset;
    $counter++;
}
foreach $key (keys %livehosts){
    print "IP Address $key is up with mac of $livehosts{$key} \n";
}

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In reply to ARP Lookups by WalkingZero

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