DHCP Renewal

[Guest]

I couldn't find a DHCP section so I posted this here. I have a Windows 2000
Server setup in AD and using DHCP for handing out some of my addresses. I am
having problems when I try to Reserve and address. For example I added a
Windows XP Laptop today and when booting it picked up an IP address with no
problem out of my general scope. But when I set up a reservation for this
laptop using its MAC address about 90% of the time the XP system says that
"Access is denied" when it tries to renew it IP address. Instead it just
assigns 0.0.0.0 for its IP address. Maybe another DHCP is on the network
that I'm not aware of. Is there any way to tell where the Laptop is trying
to retrieve an address from? Any Ideas?

Thanks,
Scotty

 

[Ryan Hanisco]

Scotty,

If it is actually getting an IP address from another DHCP address, you will
see that in the ipconfig /all output.

To really see where it is getting its DHCP requests ACK/NAK responses from,
you'll need to do a packet capture to see the entire handshake. This is the
only "real" way to track that down.

Finally remember that general users aren't allowed to drop and renew an IP
address. This would work on reboot though. You might just be seeing the
normal deny when you manually try to do something that you don't have
permissions to do.

 

[Guest]

Thanks for the reply. What kind of permissions can I give to that
computer/user that will allow me to release/renew an ip address from a
reservation?

Also, does a computer have to be part of the Active Directory Domain in
order to receive reservations?

Thanks.
Scotty

 

[Ryan Hanisco]

DHCP works on a level lower than the OS and is not aware of computer
membership or logon. This is simply a broadcast request and acceptance of
the first reply (as opposed to things like ARP that will take the last
request.) The request packet has the MAC of the source in it. The DHCP
server sees this and issues the correct IP address for the MAC based on its
reservation table.

I don't know the specific permissions that are required... perhaps someone
else here will be kind enough to help us out in that respect. (I'll try to
look when I get a chance, but can't promise anything there.) You can
understand, though, not wanting to give a normal user the ability to change
the IP settings. Rebooting the machine should get the reservation though.

 

[Guest]

I am still a little confused as to why I couldn't release/renew the adapter.
Wouldn't this do the same thing as a reboot as far as DHCP is concerned?
Thanks for the info.