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arpreset.pl
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arpreset.pl
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#!/usr/bin/perl -w
###################################################################
# arpreset 0.2
# Copyright (C) 2005 Steve Milton (milton AT isomedia.com)
#
# Utility for deleting a single ARP entry from a cisco router.
# Script adapted from description on Cisco tech article.
# http://www.cisco.com/warp/public/477/SNMP/clear_arp.shtml
#
# The Cisco router needs to have a read/write community setup
# for the utility to work. I recommend using the following
# IOS commands to setup a restricted community that can only
# work with the MAC table. You will need ENABLE level access
# to the router to execute these commands.
#
# access-list 50 permit 123.123.123.123
# access-list 50 permit 123.123.123.124
# access-list 50 deny any
# snmp-server view arpchange ipNetToMediaEntry.4 included
# snmp-server community blahblah view arpchange RW 50
#
# Set the access-list permit to the IP addresses of the systems
# you want to be able to make changes to the MAC table. Set
# the community name (above blahblah) to something random and
# password-like.
###################################################################
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
# 02110-1301, USA.
###################################################################
use strict;
use Getopt::Long;
&Getopt::Long::config('auto_abbrev');
my ($router,$community,$address,$help,$check);
$router=$community=$address=$help=$check="";
my $status = GetOptions("router:s" => \$router,
"community:s" => \$community,
"address:s" => \$address,
"help" => \$help,
"check" => \$check);
if (($status == 0) or $help) {
&PrintUsage;
exit 1;
}
if (!$router or !$community or !$address) {
&PrintUsage;
exit 1;
}
# OID for the ARP table entries
my $ciscoOID = ".1.3.6.1.2.1.4.22.1.4";
my $target = "";
# Walk the SNMP ARP table on the router to locate the target address
open(GET, "/usr/bin/snmpwalk -v1 -c $community $router $ciscoOID |");
while(<GET>) {
if (/^(.*?\.$address)\s/) {
$target = $1;
print $_;
}
}
close(GET);
if ($target and !$check) {
print "-- changed to --\n";
# set the target address to "invalid"
system("/usr/bin/snmpset -v1 -c $community $router $target i 2");
} elsif (!$check) {
print "No target OID located.";
exit 1;
}
exit;
sub PrintUsage {
print "arpreset 0.2\nCopyright (c) 2005 by Steve Milton\narpreset comes with ABSOLUTELY NO WARRANTY\n\n";
print "Usage: arpreset --router=routeraddress --community=rwcommunity --address=ipaddress\n";
print " arpreset --help\n";
print "\nWhere ipaddress is the IP address in the Cisco router that you want to invalidate\nfrom the MAC address cache.\n";
print "\nYou can add --check to the command to make it NOT update the router, but check for\nthe entry only.\n";
exit;
}