I am confused about DHCP

Timothy Murphy gayleard at eircom.net
Fri Jun 13 21:03:41 UTC 2008


Antonio M wrote:

>> > I have a small LAN with DHCP running on Fedora 9. I checked the active
>> > leases: this is the list of active leases
>> > 1)I don't understand how IP address is connected to MAC address, i.e.
>> > if
>> a
>> > MAC has already an IP address, should a new lease be started with same
>> MAC
>> > address?? I see 5 IP's connected to same MAC address
>> > 2) How are  the IP adressess released?? I would expect
>> > 192.168.0.63after 192.168.0.62 and so on... (please note that
>> > 00:16:d4:dc:a7:08 sometimes
>> is
>> > started by F9 and sometimes by F10
>>
>> What does your /etc/dhcp.conf look like, as a matter of interest?

> #
> # DHCP Server Configuration file.
> #   see /usr/share/doc/dhcp*/dhcpd.conf.sample
> #
> #
> # DHCP Server Configuration file.
> # see /usr/share/doc/dhcp*/dhcpd.conf.sample
> # dhcpd.conf
> #
> # Sample configuration file for ISC dhcpd
> #
> 
> # option definitions common to all supported networks...
> # option domain-name "fugue.com";
> # option domain-name-servers toccata.fugue.com;
> 
> # option subnet-mask 255.255.255.0;
> ddns-update-style none;
> subnet 192.168.0.0 netmask 255.255.255.0 {
>     range 192.168.0.51 192.168.0.250;
>     option subnet-mask 255.255.255.0;
>     option broadcast-address 192.168.0.255;
>     option routers 192.168.0.1;
>     option domain-name-servers 62.211.69.250 , 212.48.4.15;
>     default-lease-time 604800;
>     max-lease-time 2592000;
>     }

I'm no expert, but I put the MAC addresses of my machines in dhcpd.conf, eg
---------------------------------------------------
subnet 192.168.2.0 netmask 255.255.255.0 {

        authoritative;
        option routers                  192.168.2.2;
        option subnet-mask              255.255.255.0;

        option nis-domain               "gayleard.com";
        option domain-name              "gayleard.com";
        option domain-name-servers      159.134.237.6,159.134.248.17;

        range dynamic-bootp 192.168.2.128 192.168.2.254;
        default-lease-time 21600;
        max-lease-time 43200;

        host alfred {
                hardware ethernet 00:40:F4:6E:07:A1;
                fixed-address 192.168.2.1;
        }

        host helen {
                hardware ethernet 00:40:F4:4D:60:8A;
       }
...
}
---------------------------------------------------

But maybe this is not what you want?
I agree the IP addresses given to your machines are surprising ...






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