IP address and DHCP Server
 

Recently our clients hardly to get IP address via DHCP server than before and some times clients can not get IP address and return 169.xxx.xxx.xxx. I believe we're running out of the IP address so is there any way to know about that? Does reduce the lease time can help about this issue? We're running on Redhat Enterprise with BIND

If you've more Hosts then IP-Addresses are available for that particular netmask you'll have to create a new subnet declaration in dhcp.conf. Reducing the lease time won't solve it.

As i described above, we're running out of IP address but is there any way to know that on Linux server? Like on Window server, if the scope doesn't have enough IP addresses then it shows a exclamation point near to it so we know it has the problem. Can we do the same on Linux?

You could look at the DHCP leases file:

http://linuxreviews.org/man/dhcpd.leases/

I know it works with dhcp3-server, I'm not sure about other DHCP software.

Reducing the lease time does help if some of the machines are laptops that get moved, or systems that are turned off at various times. That frees up their IPs to be used by another station more quickly.

Edit: It's usually kept in /etc/dhcpd.conf

Chort - upon interface shutdown, the system is expected to release its lease. For machines that are yanked from the net, the reduced lease time will allow dhcpd to reuse the IP more quickly as you state.

We had a similar problem in our windows DHCP environment. One (5-6yr old!) server was handling all A D functions plus DHCP. I lowered the lease time then immediately noticed the resources would peak and stagger while narrowly keeping addresses available.

In the end we created VLAN's amd separate DHCP scope servers then got past that annoyance :)

Well that's what it's supposed to do, whether you would say it's expected is a different matter ;)