Linux – How to get the free out IPs in our IDC

linux

Our company have a IDC (Internet Data Center), and in our IDC, there are many host machines, every host has 1-3 IPs.

There is a situation, such as one host machine has 3 IPs(eg. 102.23.33.1 -> 102.23.33.3). (means in the host machine, have configured the IPs to it)

If the host machine only use 102.23.33.1, and there free out the 102.23.33.2 and 102.23.33.3. We want to find out the free IPs.

How can I do that? I tried to use the forloop to ping the whole IPs, but this is not accurate, because some host machine are baned for ping.

EDIT

I means the host machine if has 3 IPs, and all can ping them, but the host machine only use the first IP to connect with public network, how can I find the other 2 IPs host machine do not use (or do not often use)?

EDIT-2

I mean the IPs all configured on the OS but may not be actually using them.

EDIT – 3

So, all the before, there can be understood as bellow:

I have a Router, and under it, there are many host machines, and every host machine have some IPs, and how can I record the IPs that go through the Router everyday.

Is there a tool for record the IPs which get through the Router? Or how can I realize my requirement ?

Best Answer

This adds a logging rule into the iptables FORWARD chain:

# iptables -I FORWARD -j LOG --log-prefix 'MYIPS: '

This searches for the matching packets:

# grep MYIPS /var/log/syslog

The file name may depend on your Linux distribution.

And this generates a list of unique IP addresses seen by the forwarding chain in your router:

# grep -oE '(SRC|DST)=[0-9.]*' /var/log/syslog | sed 's/.*=//' | sort -u
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