Monitoring plugin to check conntrack NAT source ID address for a destination.

You could:

  • filter destination with IP address, protocol and destination port
  • check NAT source IP address against one detected from routing table
  • check number of NAT source IP address use against a limit

This script could be used as Icinga/Nagios check plugin.


  • conntrack CLI command
  • awk
  • sed


cd /usr/local/src
git clone
mkdir -p /usr/local/lib/nagios/plugins/
ln -s /usr/local/src/check_conntrack_src_addr/check_conntrack_src_addr /usr/local/lib/nagios/plugins/


Usage: ./check_conntrack_src_addr [-h|-d] -D destination [-l limit] [-c] [-f IP address]
  -h                    Show this help message
  -d                    Show debug messages
  -C                    The conntrack command path (default: /usr/sbin/conntrack)
  -S                    Use sudo to run conntrack commands
  -D [destination]      The destination IP address
  -p [protocol]         The destination procotol (ex: tcp or udp)
  -P [port]             The destination procotol port (ex: 5600)
  -c                    Check source NAT IP address against detected source IP address from route table
  -f [IP address]       If check source NAT IP address enabled, specified source IP address of connection
  -i [input interface]  If check source NAT IP address enabled, specified source input interface device
                        (default: auto-detected from source IP address)


Copyright (c) 2020 Easter-eggs


This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License version 3 as published by the Free Software Foundation.

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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.