DHCP Settings and LAN Switch Problem

["Anand Shankar" <anandsha@xxxxxxxx>]

On my LAN I give addresses with a default lease life of 1 hour. Earlier, it
was 8 hours and was working OK. When the no. of machines increased (230
machines: available dhcp addresses 200), I started getting "failed to get
DHCP address" type messages. After setting lease life of 1 hour, I notice
that there are a no. of machines shown in dhcpd.leases file, whereas the
machines are actually switched off. I notice that such addresses are
continuing in the dhcpd.leases file even after expiry of 1 hour time as also
after restarting of dhcp.

Can someone help me with a conf file such that:

As soon as (or a 10 min delay) a machine is switched off, the IP address
allocated to the machine is released from dhcpd.leases

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In a different problem, I find that a port on network switch (Intel)
occasionally hangs -- no communication; The LED on the port flicks green and
the cable continuity is OK, the client-machine connects OK from another port
on the same switch. The Network Management SW shows everything fine on the
switch. What can be the issue on the NW switch??

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Anand Shankar