DHCP leases

Lloyd Brown lloyd_brown at byu.edu
Tue Jan 29 10:33:52 MST 2013

I can't speak to how all routers implement it, but from what I know of
the protocol, it would be a poor design choice to allow re-use of IPs
before the lease expires.  The problem is that the lease time
information is sent to the client, so it's also aware of how long it can
go before it needs to re-request the IP.  If your router started handing
out non-expired IPs to new devices, then you have the potential of
multiple devices active on the network with the same IP.  That's really
not a good idea.

If you consistently have more active devices than DHCP IPs available,
then the only real solution is to increase the number of IPs available,
or decrease the number of devices.

If, however, the number of devices is lower than the number of IPs, but
new devices can't get IPs since the leases haven't expired yet, then you
can either increase the number of IPs, or decrease the lease time to get
the IPs to cycle more frequently.

Lloyd Brown
Systems Administrator
Fulton Supercomputing Lab
Brigham Young University

On 01/29/2013 10:28 AM, Wade Shearer wrote:
> So you're saying that they are always exclusive within the lease period? Are there any routers where they aren't exclusive? 

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