Home » Categories » Multiple Categories

Disabling Port 113 IDENT Requests

Problem Description

You are seeing port 113 return requests either from your Nagios XI server (when submitting NSCA passive results) to the originating host OR you are seeing port 113 return requests when checking NRPE services).

You will see this behaviour on your firewall logs as you will most likely not have a firewall rule for port 113.

 

 

Explanation

This is usually because you are running an NRPE check through XINETD with USERID included on the log_on_success or log_on_failure options in your remote hosts /etc/xinetd.d/nrpe file.

OR this could be because you are submitting passive results to the XI server through NSCA (which is running under XINETD) /etc/xinetd.d/nsca with the same options as above.

Further information can be found in the following link:

https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/4/html/Reference_Guide/s2-tcpwrappers-xinetd-alt.html#s3-tcpwrappers-xinetd-alt-log

Note that the USERID option requires an IDENT request to port 113 on the originating server to determine the USERID, that's why you're seeing it.

 

Resolution

Then remove the USERID option from the log_on_failure AND log_on_success to stop the IDENT from occurring. The file you need to change depends on:

  • NRPE on remote host
    • /etc/xinetd.d/nrpe
  • NSCA on Nagios XI server
    • /etc/xinetd.d/nsca

For example, either comment this line out or remove it completely:

# default: on
# description: NSCA (Nagios Service Check Acceptor)
service nsca
{
           flags = REUSE
           socket_type = stream        
           wait = no
           user = nagios
           group = nagios
           server = /usr/local/nagios/bin/nsca
           server_args = -c /usr/local/nagios/etc/nsca.cfg --inetd
           log_on_failure += USERID
           disable = no
           only_from = 127.0.0.1
}

 

After making the changes you need to restart the xinetd service using one of the commands below:

 

RHEL 7+ | CentOS 7+ | Oracle Linux 7+ | Debian | Ubuntu 16/18/20

systemctl restart xinetd.service

 

 

 

Final Thoughts

For any support related questions please visit the Nagios Support Forums at:

http://support.nagios.com/forum/

0 (0)
Article Rating (No Votes)
Rate this article
  • Icon PDFExport to PDF
  • Icon MS-WordExport to MS Word
Attachments Attachments
There are no attachments for this article.
Related Articles RSS Feed
Nagios XI - Downloading A System Profile
Viewed 4828 times since Wed, Jul 19, 2017
Nagios XI - Can’t Log Into The Web Interface
Viewed 40661 times since Tue, Jan 27, 2015
ERROR: Please add the ’Optional’ channel to your Red Hat systems subscriptions
Viewed 21641 times since Tue, Jan 26, 2016
XI 5.4 monitoring engine not running
Viewed 7901 times since Mon, Feb 6, 2017
NRPE - Connection Refused By Host
Viewed 12317 times since Mon, Jul 17, 2017
Nagios XI - MySQL/MariaDB - Max Connections
Viewed 25925 times since Thu, Jun 2, 2016
Nagios XI - Issues with mod_gearman and Performance Data Newlines: "\n"
Viewed 2899 times since Tue, Feb 2, 2016
Nagios XI - Event Data Is Stale
Viewed 3830 times since Wed, Jan 27, 2016
Nagios XI - Uploaded plugin returns "/bin/bash^M: bad interpreter: No such file or directory"
Viewed 5092 times since Thu, Feb 25, 2016
CCM says unapplied changes exist, but none listed
Viewed 3693 times since Mon, Feb 27, 2017