#!/usr/bin/perl
# Change the above line to match the location of Perl on your system,
# e.g. /usr/local/bin/perl or /usr/bin/perl. The command "which perl"
# should provide its location.
#
# Name: get_arp
# Version: 1.1
# Written by: JMC (support -at- moonpoint.com)
# Created: 2/1/2006
# Last modified: 7/22/2007
# Purpose: Obtain the ARP table from a network device, such as
# a Cisco router or Linux workstation.
# Usage: get_arp [--nomac] hostname community_string
#
# Arguments: 
#   1. If "-nomac" is specified on the command line, then the MAC addresses
#      corresponding to the IP addresses in the ARP table will not be displayed.
#   2. hostname should be the IP address or Fully Qualified Domain Name (FQDN)
#      for the device to be queried.
#   3. community_string should be the read-only SNMP community string for the
#      device.
#  
# Notes: 
#
# 1. This script depends on the UCD SNMP tool snmpwalk being present
#    on the system on which the script is run.
# 2. The latest version of this script is available at
#    http://support.moonpoint.com/downloads/computer_languages/perl/get_arp
# 3. For further information, see 
#    http://support.moonpoint.com/blog/blosxom/2006/02/01#get_arp
# 4. For other Perl scripts, 
#    see http://support.moonpoint.com//downloads/computer_languages/perl/

# Getopt::Long allows one to parse arguments on the command line
# See http://aplawrence.com/Unix/perlgetopts.html and
# http://www.unix.org.ua/orelly/perl/prog/ch07_035.htm for further
# information

use Getopt::Long;

# The optional "--nomac" argument controls whether MAC addresses are
# displayed along with their corresponding IP addresses. If "--help"
# is included on the command line, print usage information and quit.

&GetOptions("nomac" => \$nomac, "help" => \$help);

# Display usage information if "--help" was entered on the command line

if (defined($help)) {
   print "Usage: get_arp [--help] [--nomac] hostname community\n\n";
   print "If the optional --nomac argument is supplied, only IP addresses\n";
   print "will be displayed, rather than both IP addresses and their\n";
   print "associated MAC addresses.\n";
   exit(); 
}

# There should be at least 2 arguments, the hostname or IP address and the
# community string

if ($#ARGV < 1) {
   die "Usage: get_arp [--help] [--nomac] hostname community\n";
}

#
# Use "-v 1" to avoid "couldn't find party database" or "Bad version
# specified error messages. Previous releases of the UCD SNMP tools sent SNMPv2 
# (classic queries, which relied on party configuration information being 
# available. With the current release, by default queries now use SNMPv2c,
# which does not need any such party configuration.
# In either case, it is possible to specify the use of SNMPv1 
# instead by giving the application the option "-v 1".
#
# A reference on Object Identifiers (OID) can be found at
# http://www.alvestrand.no/objectid/1.3.6.1.2.1.html
# You can do a search for specific OIDs at that URL.
# 
# snmpwalk usage:
# snmpwalk $router $communitystring $querytype
#
# $router = IP address or name of the router
# $communitystring = Community string
# $querytype = ip.ipNetToMediaTable.ipNetToMediaEntry.ipNetToMediaPhysAddress
#

$router = $ARGV[0];
$communitystring = $ARGV[1];
$querytype = "ip.ipNetToMediaTable.ipNetToMediaEntry.ipNetToMediaPhysAddress";
$now = localtime();

$snmpresult = `snmpwalk -v 1 -c $communitystring $router $querytype`;

# For a Cisco router, snmpresult will hold results in the form below at this 
# point:
#
# ip.ipNetToMediaTable.ipNetToMediaEntry.ipNetToMediaPhysAddress.6.192.168.0.5
#  = 0:30:f2:ec:17:fc
# ...
# ip.ipNetToMediaTable.ipNetToMediaEntry.ipNetToMediaPhysAddress.6.192.168.0.5
#  = 0:30:f2:ec:8b:fc
#
# For a Linux workstation, snmpresult will hold results in the form below
# at this point:
#
# IP-MIB::ipNetToMediaPhysAddress.2.192.168.6.49 = STRING: 0:c0:7b:a2:a1:d3

# Remove all but the IP and MAC addresses

$snmpresult =~ s/.*ipNetToMediaPhysAddress\.\d*\.//g; 
$snmpresult =~ s/STRING: //g;

print "ARP table for $router on $now\n\n";

# If "--nomac" was entered on the command line,
# don't display MAC addresses. At this point snmpresult holds a list
# of IP addresses and their corresponding MAC addresses in the form 
# IP Address = MAC Address

if (defined($nomac)) {
   $snmpresult =~ s/\s=\s.*:.*:.*:.*:.*:.*//g;
}
print "$snmpresult";