Check device name

sudo lshw -class network -short

Check hardware information

lshw -C network

Change card LAN

Edit interface

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).
source /etc/network/interfaces.d/*
# The loopback network interface
auto lo
iface lo inet loopback
# The primary network interface
allow-hotplug eth0
iface eth0 inet dhcp

To disconnect a network

sudo ifconfig eth0 down

To connect a network

sudo ifconfig eth0 up

Script to keep raspberry Pi network alive:

if ifconfig eth0 | grep -q "inet"
       #echo "$(date "+%m %d %Y %T") : Ethernet OK" >> $LOGFILE
       echo "$(date "+%m %d %Y %T") : Ethernet connection down! Attempting reconnection." >> $LOGFILE
       ifconfig eth0 up
       OUT=$? #save exit status of last command to decide what to do next
       if [ $OUT -eq 0 ] ; then
               STATE=$(ifconfig eth0 | grep "inet")
               echo "$(date "+%m %d %Y %T") : Network connection reset. Current state is" $STATE >> $LOGFILE
               echo "$(date "+%m %d %Y %T") : Failed to reset ethernet connection" >> $LOGFILE

Add the script to cron

sudo nano /etc/crontab

Add this line to the end

*/3 * * * * root bash /home/pi/bin/

Check the cron service status

service cron status

Turn on the cron service

sudo service cron restart

Turn the network down

sudo ifconfig eth0 down

Check its log

less /home/pi/network-monitor.log