Using a script to populate an ipset set with DHCP addresses

[Denna]

I'm trying to create a script that adds DHCP addresses to an IP set.

1) Determine the DHCP address range with the following values.

nvram get dhcp_start = 192.168.1.2

nvram get dhcp_end = 192.168.1.4

2) Create a DHCP IP set called DHCP_CLI.

ipset create DHCP_CLI bitmap:ip range 192.168.1.0/24

3) Add all IP addresses with the range of dhcp_start and dhcp_end to the DHCP_CLI IP set.

ipset add DHCP_CLI <dhcp_start value>
...
ipset add DHCP_CLI <dhcp_end value>

In step 3, how would you iterate through the dhcp_start and dhcp_end values to add the following to the DHCP_CLI set ?

192.168.1.2
192.168.1.3
192.168.1.4​

 

[redhat27]

Step 3:

#!/bin/sh
startIP=$(nvram get dhcp_start)
endIP=$(nvram get dhcp_end)
loopIndex=${startIP##*.}
while [ $loopIndex -le ${endIP##*.} ]; do
  echo ${startIP%.*}.$loopIndex
  loopIndex=$((loopIndex+1))
done

 

[redhat27]

Note that this simple example above would work for Class C networks, and also in your OP example.
For Class B or Class A networks, it would be a longer script, an example of which can be found here

But I do not think home routers can handle bigger pool sizes of more than 253 IPs, so you should be good with a smaller script as above

 

[Denna]

@redhat27,

That's amazing !

The DHCP range would probably be less than 10.

To add each IP address to an IP set, would you replace the echo line with ...

ipset add DHCP_CLI ${startIP%.*}.$loopIndex

 

[redhat27]

@redhat27,

would you replace the echo line with ...

ipset add DHCP_CLI ${startIP%.*}.$loopIndex

Yes

 

[Denna]

@redhat27,

It works !

You are The Man !​