How to find last time DHCP reservation was active

dhcpwindows-server-2003

Within the DHCP snap-in, I have many DHCP reserverations in my list of address leases. Some of these reservations I suspect are ancient and are not being used any more. Under Address Leases, some of the leases are marked as Reservation (inactive) in the Lease Expiration column. Is there a way to see the last time that an inactive lease was indeed active?

Best Answer

If you search for the MAC address in the plain text log files at this path:

%system32%\dhcp\DhcpSrvLog.*

...you will be able to see each time that MAC address checked in with the server within the last 7 days. Note that I tried this on a Server 2000 machine -- the path may be slightly different in a 2003 environment.

To find the MAC address, you can look it up in the DHCP reservation or run ipconfig /all on the computer with the reservation.

Related Solutions

Using DHCP with Multi-Homed NICs

DHCP servers don't allow you to have multiple IP when annoucing a single MAC address. You have to user identifiers, but not every clients and servers can use them.
The usual trick is to annouce different MAC when you do the DHCP request, but with a virtual machine it is simplier to add another NIC. It is very easy to add NICs, and this is common practice.

If you want to use identifiers, in your dhclient.conf file:

interface "eth0:1" {
    send dhcp-client-identifier "xxxx-eth0:1";
}

interface "eth0:2" {
    send dhcp-client-identifier "xxxx-eth0:2";
}

Obviously, this don't work with Windows. Maybe there is another method for this OS.

How to assign DHCP leases from a script

Maybe you should take a look at dnsmasq. It can execute external and internal (LUA) scripts. The option --leasefile-ro should be what you are looking for.

http://www.thekelleys.org.uk/dnsmasq/docs/dnsmasq-man.html

Best Answer

Related Solutions

Using DHCP with Multi-Homed NICs

How to assign DHCP leases from a script

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