DHCP problem, all addresses occupied after extending pool

[Björn Johansson]

Hi all,

Last week I discovered that we had a total of 8 addresses left on our DHCP
servers. We had DHCP on two of three out of our DC's (all W2k SP4) so I
installed and added a small "backup scope" on the third DC to temporary
solve the problem. On the two other DHCP/DC's I rearranged the primary IP
with split scope on both of the servers. See
http://support.microsoft.com/default.aspx?scid=kb;en-us;280473&Product=win2000
for more info.

When done alot of bad_address appeared in leased addresses and some of the
clients got error messages but it worked for everyone and there was now
around free 35 addresses totally in the pool. But today (3 days lease time)
some clients can't get ipaddress because there is no available addresses
left! I even shut down five clients that are running DHCP.

How can this be when there are fewer DHCP clients running and more addresses
available?


Thanks in advance,

BJ

 

[deanot]

I think maybe you should make the addresses release quicker, if all the
machines log off , the address may still be active, try lowering the time
down to 8 hours and see if that helps.

 

[Björn Johansson]

Thanks for your reply. I actually lowered leasetime to 10 mins to see if it
solved the problem which was urgent at that time. Now we have around 4 free
addresses but it's still weird.

I have not found anything like it in other newsgroups, kb etc.

Thanks

/björn

 

[Björn Johansson]

Now I found the same computer using ip address from two dhcp servers, my
suspicions were right. I checked database for incosistency and refreshed it.

/Björn

 

[Björn Johansson]

The solution anyway is look into all your "Address Leases" pool and sort by
Description. Hosts that have on "This address is already in use" description
are likley to have an address lease on another DHCP server. Have a look and
you'll see that hostname appears in both with different ip addresses. Delete
the ones that are not responding to ping, almost always the ones with "This
address is already in use" in description.

Cheers,

Björn