Configuring multiple IPs on Debian – The Easy Way

I was recently tasked with adding 100+ ips to server at work. Normally we deal with smaller networks, like /28 or /29, but this guy had a /25 which is 128 IPs (125 usable) (Side Note: before you argue and tell me it should be 126 Usable, In our line of work, there are 3 unusable IPs instead of 2… Normally you have Network (first IP in range) and Broadcast (last IP in range), in our line, we add a Gateway (Second IP in range) which is not usable by a server) SO taking away all the unusable IPs, and of course the primary IP assigned to the NIC card, that results in 124 IPs needing to be assigned.

Now in CentOS system, this is easy, you simply edit the ifcfg-eth0-range0 file, add the first IP, last IP and clonenum start value, and voila, CentOS does the rest. Debian tho…. Not so easy… You have to add each device separately. Can you imagine adding each entry… Or copying and pasting and editing every entry? Trust me, its a waste of time….

auto eth0:0
iface eth0:0 inet static
  address 192.168.1.3
  netmask 255.255.255.0

auto eth0:1
iface eth0:1 inet static
  address 192.168.1.4
  netmask 255.255.255.0

...
...
...

auto eth0:123
iface eth0:123 inet static
  address 192.168.1.126
  netmask 255.255.255.0

auto eth0:0

iface eth0:0 inet static

address 192.168.1.3

netmask 255.255.255.0

auto eth0:1

iface eth0:1 inet static

address 192.168.1.4

netmask 255.255.255.0

...

auto eth0:123

iface eth0:123 inet static

address 192.168.1.126

netmask 255.255.255.0

So I decided to make myself a little script. It started off as a simple PHP script which I used on my WAMP installation on my work laptop. If you have a WAMP setup on your work machine, you can use it (copy the next bit of code) and just change the variables. It outputs the code you see above without having to manually type in each line. Just copy and paste.

<?php 
$x = 3; # first 4th octet of the ip
$y = 126; # last 4th octent of the ip
$z = 0; # the first eth0:# you wish to use, normally 0
$ip = ‘192.168.1.’; # first 3 octets of IP address to use (dont forget the last period ".")
$nm = ‘255.255.255.0’; # Netmask to use
 
while($x <= $y) {
   echo "auto eth0:$z<br/>" ;
   echo "iface eth0:$z inet static<br/>";
   echo "     address $ip$x<br/>";
   echo "     netmask $nm<br/>";
   echo "<br/>";
   $x++;
   $z++;
}
?>

<?php

$x = 3; # first 4th octet of the ip

$y = 126; # last 4th octent of the ip

$z = 0; # the first eth0:# you wish to use, normally 0

$ip = ‘192.168.1.’; # first 3 octets of IP address to use (dont forget the last period ".")

$nm = ‘255.255.255.0’; # Netmask to use

while($x <= $y) {

echo "auto eth0:$z " ;

echo "iface eth0:$z inet static ";

echo " address $ip$x ";

echo " netmask $nm ";

echo " ";

$x++;

$z++;

}

I then realized that not everyone has a WAMP installation, so how better to progress the script than to make it a Bash script which will enable you to run the script right on the server you are adding the IPs to.

Its a rough script, not real validation (use caution) but it does make a backup of the original file, in case you don’t heed my warning. It also allows you to change the file you want to modify, it defaults to the actual path of the interfaces file for Debian, but you can change to say /home/user/text.txt if you are afraid or making a mistake… then you can copy and past it in using your favourite editor (vim is mine, F-U Nano/Pico).

[UPDATE] I updated the file to have some validation, so people are not adding letter values or extremely large values to IP ranges. [/UPDATE]
Here is the code for the bash script:
Note: make sure to either name it “debian-add-ips.sh” or change line 138 to be the files name.

#!/bin/bash
# Name: Virtual Ethernet Device IP Generator
#
# Description: This script is used to generate proper entried for the /etc/network/interfaces file
# creating virtual devices like eth0:0. It promts you for all the required information before outputing
# to which every file you wish.
#
# This file must be named debian-add-ips.sh to work properly.
#
# Author: Matthew Koster

clear
echo -e 'E[1;31;40m'"==================================================================="
echo -e 'E[1;31;40m'"= ="
echo -e 'E[1;31;40m'"= E[1;37;40mThis applicaiton is used to generate virtual ethernet devices E[1;31;40m="
echo -e 'E[1;31;40m'"= E[1;37;40mon Debian based system. These sytems have entries added into E[1;31;40m="
echo -e 'E[1;31;40m'"= E[1;37;40mthe E[1;36;40m/etc/network/interfaces E[1;37;40mfile. This script will add the E[1;31;40m="
echo -e 'E[1;31;40m'"= E[1;37;40mappropriate lines tot he file for you, making it easier to E[1;31;40m="
echo -e 'E[1;31;40m'"= E[1;37;40mmultiple virtual interfaces all at once. E[1;31;40m="
echo -e 'E[1;31;40m'"= E[1;37;40mTo exit, use ctrl+c E[1;31;40m="
echo -e 'E[1;31;40m'"= ="
echo -e 'E[1;31;40m'"= E[1;37;40mCreated by: E[1;33;40mMatthew Koster E[1;31;40m="
echo -e 'E[1;31;40m'"= ="
echo -e 'E[1;31;40m'"==================================================================="; tput sgr0
echo " "
echo " "

# Ask for File location
echo -e 'E[1;33;40m'"Enter the file you wish to insert the ips into, followed by [ENTER]"; tput sgr0
read -e -p "File: " -i "/etc/network/interfaces" file
echo ""

# Ask for virtual Device name (eth0, em0, etc)
echo -e 'E[1;33;40m'"Enter the device you wish to add IPs to (ex: eth0), followed by [ENTER]"; tput sgr0
read -p "Device: " netdevice
echo " "

# ASk for staring numeber (eth0:0)
echo -e 'E[1;33;40m'"Enter the first virtual number# (normally 0), followed by [ENTER]"; tput sgr0
read -p $netdevice":" start
echo " "
while [[ ! "$start" =~ ^[0-9]+$ ]]
do
echo -e 'E[1;31;40m'"!!ERROR!!"; tput sgr0
echo -e 'E[1;33;40m'"This value has to be a number"; tput sgr0
read -p $netdevice":" start
echo ""
done

# Ask for the first 3 octets of the IP Address (ex 192.168.1)
echo -e 'E[1;33;40m'"Enter the first 3 octets of an the IP Address, folloed by [ENTER]"; tput sgr0
echo -e 'E[1;32;40m'"Example, 192.168.1 (no trailing .)"; tput sgr0
read -p "Partial IP Address: " ipaddr
echo " "

# Ask for the last octet of first IP address in sequence
echo -e 'E[1;33;40m'"Enter the last octent of first IP address, followed by [ENTER]:"; tput sgr0
echo -e 'E[1;32;40m'"Example, for 192.168.1.2 you would enter 2"; tput sgr0
read -p "Start Octet: " first
echo " "

while [[ ! "$first" =~ ^([1-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-4])$ ]]
do
echo -e 'E[1;31;40m'"!!ERROR!!"; tput sgr0
echo -e 'E[1;33;40m'"The value has to be a number between 1 and 254"; tput sgr0
read -p "Start Octet: " first
echo ""
done

# Ask for the last octet of the last IP address in sequence
echo -e 'E[1;33;40m'"Enter the last octent of last IP address, followed by [ENTER]:"; tput sgr0
echo -e 'E[1;32;40m'"Example, for 192.168.1.254 you would enter 254"; tput sgr0
read -p "End Octet: " last
echo " "

while [[ ! "$last" =~ ^([1-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-4])$ ]]
do
echo -e 'E[1;31;40m'"!!ERROR!!"; tput sgr0
echo -e 'E[1;33;40m'"The last IP address has to be a number between 1 and 254"; tput sgr0
read -p "End Octet: " last
echo ""
done

# If the last IP address is lower than the first, issue and error
while [ "$last" -le "$first" ]
do
echo -e 'E[1;31;40m'"!!ERROR!!"; tput sgr0
echo -e 'E[1;33;40m'"The last IP address has to be greater than the first..."; tput sgr0
read -p "End Octet: " last
echo ""
while [[ ! "$last" =~ ^([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])$ ]]
do
echo -e 'E[1;31;40m'"!!ERROR!!"; tput sgr0
echo -e 'E[1;33;40m'"The last IP address has to be a number between 0 and 255"; tput sgr0
read -p "End Octet: " last
echo ""
done
done

# Ask for the last octet of the netmask
echo -e 'E[1;33;40m'"Enter the last octent of the Netmask, followerd by [ENTER]"; tput sgr0
echo -e 'E[1;32;40m'"Example, for 255.255.255.240, you would use 240"; tput sgr0
read -p "Netmask: " netmask
echo " "
while [[ ! "$netmask" =~ ^([1-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-4])$ ]]
do
echo -e 'E[1;31;40m'"!!ERROR!!"; tput sgr0
echo -e 'E[1;33;40m'"The last IP address has to be a number"; tput sgr0
read -p "End Octet: " netmask
echo ""
done

# Verifiy info with user, if incorrect, restart script
clear
echo -e 'E[1;31;40m'"=========================================="; tput sgr0
echo -e 'E[1;31;40m'"= PLEASE REVIEW THE FOLLOING CAREFULLY ="; tput sgr0
echo -e 'E[1;31;40m'"=========================================="; tput sgr0
echo ""
echo -e 'E[1;33;40m'"Here is the info you entered:"; tput sgr0
echo -e 'E[1;33;40m'"File to be modified: c"; tput sgr0
echo $file
echo -e 'E[1;33;40m'"First Virtual interface: c"; tput sgr0
echo $netdevice":"$start
echo -e 'E[1;33;40m'"IP Range: c"; tput sgr0
echo $ipaddr"."$first "-" $ipaddr"."$last
echo -e 'E[1;33;40m'"Netmask: c"; tput sgr0
echo "255.255.255."$netmask
echo " "
echo -e 'E[1;33;40m'"Is this correct? [Y/N]: c"; tput sgr0
read corr

# User must enter Y or y to continue, otherwise script restarts
if [ "$corr" != y ]; then
if [ "$corr" != Y ]; then
clear
./debian-add-ips.sh
fi
fi

# Back up the file if it exists, we all make mistakes.
if [ -f "$file" ]; then
cp $file $file.bak
bkup=1
fi

# Loop the output for as many IPs as requsted
x=$start
y=$first
z=$last

while [ "$y" -le "$z" ]
do
echo "" &gt;&gt; $file
echo "auto " $netdevice:$x &gt;&gt; $file
echo "iface "$netdevice:$x" inet static" &gt;&gt; $file
echo " address "$ipaddr"."$y &gt;&gt; $file
echo " netmask 255.255.255."$netmask &gt;&gt; $file
y=$[$y+1]
x=$[$x+1]
done
clear

# Let them know where the back up is (if they have one) and cat the file for inspction
echo -e 'E[1;33;40m'"All done - Press enter to CAT the file for final inspection"; tput sgr0
if [ "$bkup" == 1 ]; then
echo -e 'E[1;33;40m'"Note - A back up for the file has been created as: c"; tput sgr0
echo $file".bak"
fi
read -p "Press any key to continue... " -n1 -s
clear
echo " "
echo -e 'E[1;33;40m'"Out put of file c"; tput sgr0
echo $file
echo ""
echo -e "E[1;31;40m============================================================================================"; tput sgr0
echo ""
cat $file
echo ""
echo -e "E[1;31;40m============================================================================================"; tput sgr0
echo ""
echo "Virtual Ethernet IP Generation complete."
echo ""

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#!/bin/bash

# Name: Virtual Ethernet Device IP Generator

# Description: This script is used to generate proper entried for the /etc/network/interfaces file

# creating virtual devices like eth0:0. It promts you for all the required information before outputing

# to which every file you wish.

# This file must be named debian-add-ips.sh to work properly.

# Author: Matthew Koster

clear

echo -e 'E[1;31;40m'"==================================================================="

echo -e 'E[1;31;40m'"= ="

echo -e 'E[1;31;40m'"= E[1;37;40mThis applicaiton is used to generate virtual ethernet devices E[1;31;40m="

echo -e 'E[1;31;40m'"= E[1;37;40mon Debian based system. These sytems have entries added into E[1;31;40m="

echo -e 'E[1;31;40m'"= E[1;37;40mthe E[1;36;40m/etc/network/interfaces E[1;37;40mfile. This script will add the E[1;31;40m="

echo -e 'E[1;31;40m'"= E[1;37;40mappropriate lines tot he file for you, making it easier to E[1;31;40m="

echo -e 'E[1;31;40m'"= E[1;37;40mmultiple virtual interfaces all at once. E[1;31;40m="

echo -e 'E[1;31;40m'"= E[1;37;40mTo exit, use ctrl+c E[1;31;40m="

echo -e 'E[1;31;40m'"= ="

echo -e 'E[1;31;40m'"= E[1;37;40mCreated by: E[1;33;40mMatthew Koster E[1;31;40m="

echo -e 'E[1;31;40m'"= ="

echo -e 'E[1;31;40m'"==================================================================="; tput sgr0

echo " "

# Ask for File location

echo -e 'E[1;33;40m'"Enter the file you wish to insert the ips into, followed by [ENTER]"; tput sgr0

read -e -p "File: " -i "/etc/network/interfaces" file

echo ""

# Ask for virtual Device name (eth0, em0, etc)

echo -e 'E[1;33;40m'"Enter the device you wish to add IPs to (ex: eth0), followed by [ENTER]"; tput sgr0

read -p "Device: " netdevice

echo " "

# ASk for staring numeber (eth0:0)

echo -e 'E[1;33;40m'"Enter the first virtual number# (normally 0), followed by [ENTER]"; tput sgr0

read -p $netdevice":" start

echo " "

while [[ ! "$start" =~ ^[0-9]+$ ]]

echo -e 'E[1;31;40m'"!!ERROR!!"; tput sgr0

echo -e 'E[1;33;40m'"This value has to be a number"; tput sgr0

read -p $netdevice":" start

echo ""

done

# Ask for the first 3 octets of the IP Address (ex 192.168.1)

echo -e 'E[1;33;40m'"Enter the first 3 octets of an the IP Address, folloed by [ENTER]"; tput sgr0

echo -e 'E[1;32;40m'"Example, 192.168.1 (no trailing .)"; tput sgr0

read -p "Partial IP Address: " ipaddr

echo " "

# Ask for the last octet of first IP address in sequence

echo -e 'E[1;33;40m'"Enter the last octent of first IP address, followed by [ENTER]:"; tput sgr0

echo -e 'E[1;32;40m'"Example, for 192.168.1.2 you would enter 2"; tput sgr0

read -p "Start Octet: " first

echo " "

while [[ ! "$first" =~ ^([1-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-4])$ ]]

echo -e 'E[1;31;40m'"!!ERROR!!"; tput sgr0

echo -e 'E[1;33;40m'"The value has to be a number between 1 and 254"; tput sgr0

read -p "Start Octet: " first

echo ""

done

# Ask for the last octet of the last IP address in sequence

echo -e 'E[1;33;40m'"Enter the last octent of last IP address, followed by [ENTER]:"; tput sgr0

echo -e 'E[1;32;40m'"Example, for 192.168.1.254 you would enter 254"; tput sgr0

read -p "End Octet: " last

echo " "

while [[ ! "$last" =~ ^([1-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-4])$ ]]

echo -e 'E[1;31;40m'"!!ERROR!!"; tput sgr0

echo -e 'E[1;33;40m'"The last IP address has to be a number between 1 and 254"; tput sgr0

read -p "End Octet: " last

echo ""

done

# If the last IP address is lower than the first, issue and error

while [ "$last" -le "$first" ]

echo -e 'E[1;31;40m'"!!ERROR!!"; tput sgr0

echo -e 'E[1;33;40m'"The last IP address has to be greater than the first..."; tput sgr0

read -p "End Octet: " last

echo ""

while [[ ! "$last" =~ ^([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])$ ]]

echo -e 'E[1;31;40m'"!!ERROR!!"; tput sgr0

echo -e 'E[1;33;40m'"The last IP address has to be a number between 0 and 255"; tput sgr0

read -p "End Octet: " last

echo ""

done

# Ask for the last octet of the netmask

echo -e 'E[1;33;40m'"Enter the last octent of the Netmask, followerd by [ENTER]"; tput sgr0

echo -e 'E[1;32;40m'"Example, for 255.255.255.240, you would use 240"; tput sgr0

read -p "Netmask: " netmask

echo " "

while [[ ! "$netmask" =~ ^([1-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-4])$ ]]

echo -e 'E[1;31;40m'"!!ERROR!!"; tput sgr0

echo -e 'E[1;33;40m'"The last IP address has to be a number"; tput sgr0

read -p "End Octet: " netmask

echo ""

done

# Verifiy info with user, if incorrect, restart script

clear

echo -e 'E[1;31;40m'"=========================================="; tput sgr0

echo -e 'E[1;31;40m'"= PLEASE REVIEW THE FOLLOING CAREFULLY ="; tput sgr0

echo -e 'E[1;31;40m'"=========================================="; tput sgr0

echo ""

echo -e 'E[1;33;40m'"Here is the info you entered:"; tput sgr0

echo -e 'E[1;33;40m'"File to be modified: c"; tput sgr0

echo $file

echo -e 'E[1;33;40m'"First Virtual interface: c"; tput sgr0

echo $netdevice":"$start

echo -e 'E[1;33;40m'"IP Range: c"; tput sgr0

echo $ipaddr"."$first "-" $ipaddr"."$last

echo -e 'E[1;33;40m'"Netmask: c"; tput sgr0

echo "255.255.255."$netmask

echo " "

echo -e 'E[1;33;40m'"Is this correct? [Y/N]: c"; tput sgr0

read corr

# User must enter Y or y to continue, otherwise script restarts

if [ "$corr" != y ]; then

if [ "$corr" != Y ]; then

clear

./debian-add-ips.sh

# Back up the file if it exists, we all make mistakes.

if [ -f "$file" ]; then

cp $file $file.bak

bkup=1

# Loop the output for as many IPs as requsted

x=$start

y=$first

z=$last

while [ "$y" -le "$z" ]

echo "" >> $file

echo "auto " $netdevice:$x >> $file

echo "iface "$netdevice:$x" inet static" >> $file

echo " address "$ipaddr"."$y >> $file

echo " netmask 255.255.255."$netmask >> $file

y=$[$y+1]

x=$[$x+1]

done

clear

# Let them know where the back up is (if they have one) and cat the file for inspction

echo -e 'E[1;33;40m'"All done - Press enter to CAT the file for final inspection"; tput sgr0

if [ "$bkup" == 1 ]; then

echo -e 'E[1;33;40m'"Note - A back up for the file has been created as: c"; tput sgr0

echo $file".bak"

read -p "Press any key to continue... " -n1 -s

clear

echo " "

echo -e 'E[1;33;40m'"Out put of file c"; tput sgr0

echo $file

echo ""

echo -e "E[1;31;40m============================================================================================"; tput sgr0

echo ""

cat $file

echo ""

echo -e "E[1;31;40m============================================================================================"; tput sgr0

echo ""

echo "Virtual Ethernet IP Generation complete."

echo ""

Now again, its a rough script… Definitely can be improved. But it gets the job done.

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