device grabbing IP

Hopefully someone has some advice for me on this ...
We have a device on our network (which we can't track down - we think it is
a router??) that grabs available IP addresses. Because of this - and to
keep other un-approved devices off our network, we keep our IPs limited to
only those we need.
What has happened is that we released an IP, before renewing it - the rouge
device had already grabbed the IP.
I deleted the device, but it is not letting go of the address???
Now when we try to get the address back it returns a Bad Address error
saying "IP already in use".
The device name/IP doesn't show up in DHCP. We can't ping the number to
trace it.
I can't delete it.
Is there someway to force freeing up an IP that seems to be held by an
unknown device, when it doesn't show up in DHCP???
Thanks in advance for your time and sharing your knowledge.....
--
Cindy B

"Cindy B" wrote:

> Hopefully someone has some advice for me on this ...
> We have a device on our network (which we can't track down - we think it is
> a router??) that grabs available IP addresses. Because of this - and to
> keep other un-approved devices off our network, we keep our IPs limited to
> only those we need.
> What has happened is that we released an IP, before renewing it - the rouge
> device had already grabbed the IP.
> I deleted the device, but it is not letting go of the address???
> Now when we try to get the address back it returns a Bad Address error
> saying "IP already in use".
> The device name/IP doesn't show up in DHCP. We can't ping the number to
> trace it.
> I can't delete it.
> Is there someway to force freeing up an IP that seems to be held by an
> unknown device, when it doesn't show up in DHCP???
> Thanks in advance for your time and sharing your knowledge.....
> --
> Cindy B

Many routers and firewalls have built-in DHCP servers which must be disabled
before use in a domain with a DHCP server.

Sounds to me like this may not have been done for your suspect router.

The LAN side of the router should have a reserved address in the LAN DHCP,
the router should be configured to use this reserved address, with DHCP
server and client disabled. (Or no IP, DHCP server disabled, DHCP client
enabled).
--
Regards,
Newell White

Hi,
you should give a brief instruction of your network structure, so one can
think over it to be working on a small network or on a world wide net with
thousands of millions of clients.
This or that the strategy would be slightly different, i think.

On to
http://www.computing.net/windowsnt/w...rum/15074.html
it might be a device not "grabbing", but telling of (cached) bad ip
adresses.
Sniffing the DHCP operation on a client requesting a lease then could help
(if not at all).
You should see who ever is invoked!

jk