Tcpdump is getting to traffic on a network, refer tcpdump from the link :

The current developments version of tcpdump and libpcap is free from the GitHub, You can clone the tcpdump GitHub repository using

    git clone https://github.com/the-tcpdump-group/tcpdump.git
            
    git clone https://github.com/the-tcpdump-group/libpcap.git
            
You can then configure and compile the source via the normal GNU autoconf method.

The simple shell script do take a backup current tcpdump logs  every 10 minutes into a tcpdump.log in your home directory



#!/bin/bash

/usr/sbin/tcpdump -i eth0 ip >> ~/tcpdump.log &

sleep 5m

pkill -9 tcpdump


If you would like to set the cron job every 10 minutes,

Open a crontab file



# vim /etc/cron/crontab

 

0,10,20,30,40,50 * * * *  /bin/sh /root/check_tcpdump.sh

You might restart the cron service.