Which IPs from the range are assigned to DHCP enabled clients

Linux and Unix-Like Red Hat
1

Hi All

dhcpd.conf has a range of IPs sa for example( 192.168.1.201 192.168.1.220)

So this is the range of IP addresses the server will issue to DHCP enabled PC clients booting up on the network

How do i know which IPs are being used or which IPs from the range are assigned to dhcp enabled clients ?

Thanks

2 
arp -an
3

Thank you Tony.

4

Hi all
When DHCP server assign a IP to dhcp enabled clients it reserve IPs for the time specified in the dhcp.conf file and I have set it to 24 hours.

Very often DHCP server runs out of IPs so is there a way to release the IP from the client which are not pingable or down?

Or is there a script to handle this situation?

Please let me know.
Thanks

5

You could set your dhcp lease time to a shorter duration

dhcpd.leases (Linux Reviews)

Linux Tutorial - Linux DHCP Server Configuration

6

Thanks

Can I delete the entry from dhcpd.leases for the host which says "binding state free" ?
Thanks

7

It is not recommended, and I am not sure what the ramifications for that would be. You could restart the service after making the changes

8

binding state free does not mean that the lease is not in use. A binding state statement declares the lease's binding state. When the DHCP server is not configured to use the failover protocol, a lease's binding state will be either active or free. The failover protocol adds some additional transitional states, as well as the backup state, which indicates that the lease is available for allocation by the failover secondary.

Your best approach is to reduce the lease duration time.

9

Correct.

The DHCP client will try to establish a new lease if that client is still active, so this approach works best, if you don't have more address space to allocate.

Or you could allocate more address space, since it is free and cheap (when you are using NAT, that is).

10

Thanks all,
I set lease time to 12 hours in dhcp.conf.

default-lease-time 43200;
max-lease-time 86400;

---------- Post updated at 07:05 PM ---------- Previous update was at 01:38 PM ----------

Hi

One more question:
Is there a command or way to find how many IPs are available that can be assigned to dhcp enabled clients from the DHCP server.

11

Have a look at DHCPstatus. It is available on SourceForge and elsewhere. Consists of Perl scripts which parse dhcpd.conf and dhcpd.leases and displays status information, including the number of IP addresses in the dynamic pool that are free.

12

Thanks
DHCPstatus worked.Thanks