On Thu, Apr 07, 2005 at 09:52:46AM -0400, Chris Wolf wrote:
> To what extent is a computer that is registered for MSU's DHCP guaranteed to get the same IP address every time it connects in the same building?
> I thought I was told several years ago that the IP would always be the same until the registration lapsed. Now we are seeing cases where the IP address changes between one day and the next (e.g. from 35.10.156.m to 35.10.156.n). Is this a case of the DHCP server running out of available addresses and being forced to reuse an address that it otherwise would have "reserved" for the last computer it had been assigned to?
The only guarantee for an IP address from a DHCP server is for the duration
of the lease. The lease time for faculty/staff offices is typically 48 hours.
If the computer is active towards the end of that lease, it will renew the
lease for another 48 hours, with the same IP address.
If the lease expires while the computer in question is turned off, then a
new lease is established the next time the computer is back on the network.
In general, the same IP address will be assigned, if it has not been
assigned to another computer.
There are a couple factors that can cause "IP churn" such as you are
describing. One is where the number of free leases is low, causing
the DHCP server to quickly recycle the IP addresses from expired leases.
This is something we monitor daily on our DHCP server, and I know that
Ag Hall has not showed up on that list anytime recently.
The other cause of IP churn comes from a computer that does not properly
adhere to the DHCP lease rules, and holds onto an IP address too long,
or otherwise misuses one or more IP addresses which are assigned to the
DHCP lease pool.
I would suspect that one or more misbehaving computers are causing the IP
churn you report. If you can give me the specifics from one of the computers
where you are observing this behavior, I can look into it.
Doug Nelson, Network Manager | [log in to unmask]
Academic Computing and Network Services | Ph: (517) 353-2980
Michigan State University | http://www.msu.edu/~nelson/