编写 bash 脚本将给定的 su.net 细分为预定义数量的较小 su.net

Question

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Question: Write a bash script to subdivide an given su.net into a pre-defined number of smaller su.nets.

After division IP addresses shouldn't be wasted, ie accumulation of your subdivisions should make up the divided su.net.

Every su.net has 3 IP addresses reserved and not usable by hosts:.network, broadcast, gateway.

Show.network/broadcast address, number of hosts and assign gateway. Gateway should be first IP available in divided su.net. Examples:

INPUT: ./su.netter.sh 192.168.0.0/24 3

OUTPUT:

subnet=192.168.0.0/25   network=192.168.0.0   broadcast=192.168.0.127 gateway=192.168.0.1   hosts=125 
subnet=192.168.0.128/26 network=192.168.0.128 broadcast=192.168.0.191 gateway=192.168.0.129 hosts=61 
subnet=192.168.0.192/26 network=192.168.0.192 broadcast=192.168.0.255 gateway=192.168.0.193 hosts=61

INPUT: ./su.netter.sh 192.168.0.0/24 4

OUTPUT:

subnet=192.168.0.0/26   network=192.168.0.0   broadcast=192.168.0.63  gateway=192.168.0.1   hosts=61 
subnet=192.168.0.64/26  network=192.168.0.64  broadcast=192.168.0.127 gateway=192.168.0.65  hosts=61 
subnet=192.168.0.128/26 network=192.168.0.128 broadcast=192.168.0.191 gateway=192.168.0.129 hosts=61 
subnet=192.168.0.192/26 network=192.168.0.192 broadcast=192.168.0.255 gateway=192.168.0.193 hosts=61

INPUT: ./su.netter.sh 10.55.10.64/28 2

OUTPUT:

subnet=10.55.10.64/29   network=10.55.10.64   broadcast=10.55.10.71   gateway=10.55.10.65   hosts=5
subnet=10.55.10.72/29   network=10.55.10.72   broadcast=10.55.10.79   gateway=10.55.10.73   hosts=5

First of all, I am trying to analyse what logic is used to divide the su.nets. Secondly, I am trying to use the ipcalc command to get outputs but no luck.

Thanks

Answer 1

Here is the bash script, I have tried my hands on: Should work fine. The script takes 2 arguments, CIDR block and number of su.nets to divide into.

      #!/bin/bash

      cidr=$1
      total_subnet=$2
      nw_addr=`echo $cidr | awk -F'/' '{ print $1 }'` # retrieving network IP from input 1
      nw_mask=`echo $cidr | awk -F'/' '{ print $2 }'` # retrieving network mask from input 1
      dbit=`echo $nw_addr | awk -F'.' '{ print $4 }'` # retrieving the D-bit from network ( A.B.C.D )
      significant_bit=`echo $nw_addr | awk -F'.' 'BEGIN {OFS = ""}{print $1,".",$2,".",$3 }'` # retrieving A.B.C bits from n/w address

      change_bit=$(( 32 - $nw_mask)) 
      max_addr=$(( 2 ** $change_bit)) # calculating maximum addresses available in the network that can be subdivided
      dbit_max=$dbit 

      # A Funtion to calculate the least power of 2 that is equal or greater than the argument
      least_greater_power_of_two()
      {
      next_power=2
      power=1
      subnet_range=$1
      while [ $next_power -lt $subnet_range  ]; do

       power=$(($power+1))
       next_power=$(( 2 ** $power))
      done

      }

      #initialising Loop Variables
      remaining_addr=$max_addr
      max_subnet_dbit=$dbit
      total_subnet_addr=0
      starting_dbit=$dbit
      i=$total_subnet


      while [ $i -gt 0 ]; do
        starting_dbit=$(( $starting_dbit + $total_subnet_addr )) #Finding the starting D bit of the subnet

        #finding the total number of addresses in the subnet 
        subnet_range=$(( $remaining_addr /  $i )) 
        least_greater_power_of_two $subnet_range 
        total_subnet_addr=$(( 2 ** $power ))

        max_subnet_dbit=$(( $max_subnet_dbit + $total_subnet_addr ))
        remaining_addr=$(( $remaining_addr - $total_subnet_addr ))  # Remaining addresses left to be assigned to the other subnets

        last_dbit=$(( $max_subnet_dbit - 1)) #calculating last D bit in the subnet range
        subnet_mask=$(( $change_bit - $power + $nw_mask )) #calculating the subnet mask
        gateway_dbit=$(( $starting_dbit + 1 )) # calculating the Gateway D bit
        total_hosts=$(( $total_subnet_addr - 3 )) # calculating the Total-hosts in the network
        echo "Subnet= $significant_bit.$starting_dbit/$subnet_mask Network=$significant_bit.$starting_dbit Broadcast=$significant_bit.$last_dbit Gateway= $significant_bit.$gateway_dbit Hosts=$total_hosts"
        i=$(($i-1)) # updating loop variable

      done

Answer 2

I believe I have done 70% of the stuff that you require off the script. Since you were using ipcalc, dediced to use a similar binary. To start off, do the following:

yum install sipcalc if you have a RPM based OS or apt-get install sipcalc depending on the distro of your Linux OS.

Then write the following script and save it as su.netter.sh and give it 'x' permissions so that it can be executed.

#!/bin/bash

if [ $# == 0 ]; then
echo "Usage: ./subnetter.sh  IP/SUBNET RANGE"
exit
fi

subnet=$1
network=`echo $subnet | cut -d / -f1`
broadcast=`/usr/bin/sipcalc $1 | grep -i broadcast | cut -d '-' -f2`
gateway=`/usr/bin/sipcalc $1 | grep -i usable | awk '{print $4}'`
hosts=`/usr/bin/sipcalc $1 |  grep -i addresses | cut -d '-' -f2`

echo "subnet =" $subnet "network =" $network "broadcast =" $broadcast "gateway =" $gateway "hosts =" $hosts

Output of my script:

[root@puppet ~]# ./subnetter.sh  192.168.0.0/24
subnet = 192.168.0.0/24 network = 192.168.0.0 broadcast = 192.168.0.255 gateway = 192.168.0.1 hosts = 256

Please note that the requirement of the third argument is very simple and can be simply done using a for loop. I expect you to do that.

You can use the following tool to make sure that your output is correct: http://www.su.net-calculator.com/su.net.php.net_class=C

Answer 3

I have gone through the above requirment and below is what i have programmed to achieve the result.

Python Code integrated with the above shell script to achieve the result as users are expecting

Below code will create sub su.net for the existing su.net and then will call the shell script to perform the operation in loop and will provide records based on the users request.

#

#!/bin/bash

for res in `cat hst.txt` ; do

subnet=$res
network=`echo $subnet | cut -d / -f1`
broadcast=`/usr/bin/sipcalc $res | grep -i broadcast | cut -d '-' -f2`
gateway=`/usr/bin/sipcalc $res | grep -i usable | awk '{print $4}'`
hosts=`/usr/bin/sipcalc $res |  grep -i addresses | cut -d '-' -f2`

echo "subnet =" $subnet "network =" $network "broadcast =" $broadcast "gateway =" $gateway "hosts =" $hosts

done

# #

Code2

 #./bin/bash for res in `cat hst;txt` ; do su.net=$res.network=`echo $su.net | cut -d / -f1` broadcast=`/usr/bin/sipcalc $res | grep -i broadcast | cut -d '-' -f2` gateway=`/usr/bin/sipcalc $res | grep -i usable | awk '{print $4}'` hosts=`/usr/bin/sipcalc $res | grep -i addresses | cut -d '-' -f2` echo "su.net =" $su.net .network =" .network "broadcast =" $broadcast "gateway =" $gateway "hosts =" $hosts done

#

Sample Out from the result ###