Services

I've noticed that DHCP leases are being requested by clients at half the value of the default lease time.

For instance, using m0n0wall's default settings for the DHCP Server:

Default Lease Time:  7200 sec
Max Lease Time:  86400 sec

the clients (all which are Win XP or Win 2003) will send a DHCPREQUEST at 3600 sec intervals.  Is this normal?  Shouldn't clients make the request at 7200 sec?  It's annoying to see duplicated leases handed out in the DHCP lease table.

Here's a screen shot:

(http://www.geocities.com/globalrevolt/m0n0_dhcp_default.PNG)

I'm using m0n0wall cdrom 1.23 and the problem exists even if I change the Default Lease Time to other values.

After reading about DHCP on Microsoft's website, it appears that the DHCP client goes through a Renewing State at 50% of the lease time.  A key value in the Windows Registry called DhcpRetryTime appears to verify this.

However, one would expect the DHCP server to automatically expire a lease that it has just renewed -- even if time remains on the lease.  Does m0n0wall's dhcpd have a parameter that can adjust this behavior?

brgangoo,
Did you ever find any resolution to this?  I realize its been a while since the last post....

Wow, I hate bring back this old thread of mine, but I haven't resolved this issue yet and it appears it still exists in the latest stable version (v1.235).

It's not a problem, this is just how DHCP works, with any OS and any server. The DHCP standard specifies clients first attempt to renew a lease at 50% of lease length, which is exactly what is happening. This way if their first renewal attempt fails (DHCP server unavailable, network problem, etc.), they still have half the lease time to continue to attempt to renew. If you want them to renew less frequently, increase your lease time. They're renewing at half your default lease time, which is what is supposed to happen.