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How to find active DHCP server reservations?

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dachshund-digital
Posts: 40
Joined: 2021-12-23 22:22

How to find active DHCP server reservations?

#1 Post by dachshund-digital »

How to find active DHCP server reservations? Not sure where to post this question, but figured here was a starting point.

This not a question to list dynamic ip address assignment, via a defined address pool, but ip addresses that are reserved, via explicit reservation in the isc-dhcp-server configuration.

The typical perl script, dhcp-lease-list, can only show dynamically assigned ip addresses, via the dhcp lease file on the isc-dhcp-server of course. But how does anyone find the active ip addresses that are done via host records, in the dhcp server configuration file, i.e. explicit ip reservation? An ip address via reservation is still provided by the isc-dhcp-server of course. Parsing the log files seems on way possible, but there has to be a better, more elegant, method, no?

Kassebasse
Posts: 11
Joined: 2022-04-19 21:19

Re: How to find active DHCP server reservations?

#2 Post by Kassebasse »

Can you please explain what you mean a little bit better?
For starters, what IP addresses scope are we talking about?
I mean;
192.168.0.1 - 192.168.0.255 with a /24 (255.255.255.0) netmask
are you wondering what ip-addresses are used or what scope?
Note: I am not a linux expert by any means, but I have knowledge about networking.

arzgi
Posts: 1185
Joined: 2008-02-21 17:03
Location: Finland
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Re: How to find active DHCP server reservations?

#3 Post by arzgi »

nmap, I use

Code: Select all

nmap -sP 192.168.1.0/24
But be sure to be behind NAT, or you get angry messages from you ISP :mrgreen:

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