A simple perl script using Net::MAC:Vendor to find vendors from ethernet MAC addresses in the ARP table. On ubuntu you need this dependancy: libnet-mac-vendor-perl

arp_mac_vendor.pl

use Net::MAC::Vendor;
use strict;

open(ARP, "arp -n|") || die "Failed $!\n";

my @arp_table;
while (<ARP>) {
  if ($_ =~ m/incomplet/) {next;}
  if ($_ =~ m/Address/) {next;}
  my @line = split(' ',$_);
  my $computer = {};
  $computer->{ip} = $line[0];
  $computer->{mac}  = $line[2];
  $computer->{if}  = $line[4];
  # Get vendor info
  my $vendor_info = Net::MAC::Vendor::lookup( $computer->{mac} );
  $computer->{vendor} = $vendor_info->[0];
  push @arp_table , $computer;
}

print "ARP Table with vendors:\n";
for my $i (0 .. $#arp_table) {
  print "$arp_table[$i]{ip}\t";
  print "$arp_table[$i]{if}\t";
  print "$arp_table[$i]{mac}\t";
  print "$arp_table[$i]{vendor}";
  print "\n";
}