eth1 connection of two servers in Debian

In order of connect two Debian servers  to comminucate through eth1 connect them using ethernet cable and use these settings in /etc/network/interfaces


===
backend

auto eth1
iface eth1 inet static
        address 192.168.1.1
        netmask 255.255.255.0
        mtu 9000


======
frontend

auto eth1
iface eth1 inet static
        address 192.168.1.2
        netmask 255.255.255.0
        mtu 9000

Useful commands to analyse access.log

Include and exclude strings in search term:

grep -F "google"  /var/log/nginx/access.log | grep -v "33.44.55.66"  > google.txt

Get unique IPs:

awk '{print $1}' google.txt|sort -u

Or in a single line:

grep -F "google"  /var/log/nginx/access.log > googl.txt && awk '{print $1}' google.txt|sort -u

 ---------------------------

Convert list of IPs to unique IP blocks for nginx deny:

sed -i -e   's/$/;/' file.txt && sed -i -e   's/[0-9]\?[0-9]\?[0-9];$/0\/24;/' file.txt &&  sed -i -e   's/^/deny /' file.txt | sort -u


Add 'deny' to the begining of each line of a file:

 sed -i -e   's/^/deny /' file.txt

Add ';' at the end of each line of a file:

sed -i -e   's/$/;/' file.txt

Now convert IPs to 24 blocks:

 sed -i -e   's/\.*;/.0\/24;/' file.txt

Perpare deny list in one line:

sed -i -e   's/$/;/' file.txt && sed -i -e   's/[0-9]\?[0-9]\?[0-9];$/0\/24;/' file.txt &&  sed -i -e   's/^/deny /' file.txt