I have a question regarding dhcp... What i found is that the company's existing setup was just dynamically assigning address out of the pool, and the lease expiration time was set to never. I changed the lease expiration time to 12 hours, thinking that if i make a reservation for a particular mac address, then the computer would get that address assigned when the person starts their computer in the morning, then they could user their computer all day, and the lease would expire later that evening. then if i were to change the ip address in the reservation, i could have the user get that address when they turned on the computer the next day. of course, leave it to microsoft to make things that dont work the way it seems they ought to... :) either that or i dont fully understand the microsoft way when it comes to dhcp leases. What happens instead is that i make a bunch of reservations for various computers which are set to get their addresses dynamically. there many win98, winme, win2k, and winxp workstations. I have one machine that is supposed to get an address due to a reservation, and another machine that is supposed to get a different address due to a reservation. the first machine is a brand new installation and has no option to get the address the dhcp server wants to give it. however the second machine was previously assigned the same ip before i changed the dhcp settings. What happens is that the second machine, which is win98 does not get assigned the ip that it's reservation says, it just keeps the same ip it already had. What's worse, is the dhcp server detects this and DISABLES the reservation for the machine that is SUPPOSED to have the ip, by changing the mac address to something like 000000000001 and making the comment something like "disabled because the ip exists on the network". So now the machine that is supposed to have the ip will never get it again until i manually go in and fix it. That is completely stupid, because it means that anyone can steal an ip and cause the server to break for the person who's ip they stole. Also, this is only one case. there are several cases of this on the network. So i have to go around to each computer, manually reset the ip's to dynamic and force them to renew their lease. That sounds very detremental to the whole point of having dhcp in the first place. Basically it looks like not even using dhcp can prevent me from walking around to each and every computer and doing things manually. can anyone offer helpful advice on this?

Only last week, I moved my company over from static IP to dhcp. (This, by the way reduces network traffic by up to two thirds, so is worth working on) I needed to reserve the IP address of my mailserver, so after creating the reservation on the MAC address of the card, I needed to remove the mailservers listing in DHCP and DNS on the server before it would allow the placement of the reservation, I don't know if it that is the MS way, or I just got lucky? It has however been fine ever since. hope it helps

Like most that don't understand a process, you blame Microsoft. Your question is worded so poorly it's hard to follow but see if this helps. If an address already exists on the network whether it was assigned dynamically or staticly, it will not be handed out via a reservation. When an address is assigned to a client, the client will do what's called a gratuitous ARP to see if the address is already in use. If so, it will return a BAD_ADDRESS reply to the server. If the lease time expires on a client, the client will still try to obtain the same address again and will get it if the address is available. It will also renew the address after half of the lease time has expired. So in your scenario, it will renew the address after 6 hours and it will be good for another 12. If you want to set this up correctly, make sure your reservations come from a range of IP address that are not already in use. When set up properly, it works great. If you are trying to set reservations for addresses already in use, it's going to fail. It's like owning a restaurant and telling people they can walk and sit wherever they want, but yet still taking reservations and wondering why the people with a reservation are pissed when someone is sitting at their table. You can't have it both ways. An address that is reserved will not be handed out via DHCP but the server also does not know which addresses are already staticly assigned.

first of all, sorry for the poor wording. i was tired, and i even left one issue out. Secondly, i wasn't really blaming microsoft, that was just a joke. Anyway, ok, i got the part about not assigning an address that already exists. I expect that. But the thing is, none of the computers on the network were static ip. There were all using dhcp. The way the dhcp was before, there was just an address pool that was getting used, and i wanted to setup reservations to give the same ip out each time according to mac address. To clarify, what happened was i changed the lease time from 'never' to '12 hours' before making any changes and let things go for a couple days. when I began changing ip's, computers would not get the newly assigned ip as a result of the reservation. they would simply keep the ip they had originally been assigned. even across multiple power downs and reboots. This symptom primarily existed on win98 machines. I thought that the machine should request an address from the dhcp server when it first boots, regardless of what it may have been assigned in the past, before shutting it down, though i could be wrong about that. this reason is what caused some of the reservations to become broken. Example. Lease time on dhcp server = never. change to 12 hours. wait 2 days. delete existing assignment from the address assignments list. create reservation for this computer. when computer turns on next, dhcp server seems to think it should be assigning the ip from the reservation. dhcp server does not assign the original address the computer had before this process. computer still has the original address before this process. second computer tries to request address from dhcp server. dhcp server tries to assign address according to reservation for second computer. dhcp server discovers ip address in reservation is already in use on network. assignment fails. dhcp server permanently disables reservation. The only authoritative entity that seems logical for determining what ip the second computer should get is the dhcp server, with the reservation configured. I understand not assigning an ip that already is in use, i expect that, i just wish it wouldn't permanently break the reservation. The think that gets me the most is that the first computer should have said "what ip am i" and the server should have said "this" but in reality that did not happen. so the first computer had an ip that it should not have had, causing problems for the computer that the ip was reassigned to. I would like all the computers on the network (which are all set to use dhcp) to have their ip controled at the dhcp server. if i decide one computer should have a different ip, i want to change it at the dhcp server, reboot the computer, and have the computer get the new address. I am normally a fan of static IP for these reasons: 1. it works. you set the ip and there you go. as long as you're a good sysadmin and you do it right, you never have any problems. 2. less broadcast traffic occurs since no dhcp communications take place. I am switching to dhcp for management purposes, as I figured with a network of 35 machines, it might be easier to control with dhcp. Ultimately the problem has been solved, by first entering all the reservations and then secondly going to each computer, ensuring proper network settings, and performing ipconfig /release followed by ipconfig /renew

about the part i left out... after i got everything solved I discovered another problem. Every morning when people came in and turned on their computers, they would not work. no one had any network access, not to the file server, the internet, printers, or anything. I discovered that the computers were simply not getting an ip assignment, and instead of using the normal windows auto ip setup experimental address or whatever, they were just 0.0.0.0. It was also discovered that after people bitched, resetting the server solved the problem, but WITHOUT rebooting the workstations. I theorized that when the lease expires, that's it. it's expired. for good. too bad. although i strongly believe that is not the case, that is the way it behaved. when i changed the lease time from 12 hours back to never my problems vanished. however, now i fear that if i need/want to change a machine's ip, when i change it in the reservation, that will just be ignored as it was when this all started, and i will be back to the same problem as before. what i want out of dhcp is NOT something that is basically the same as static, in that i have to do just as much troubleshooting and cofiguring on each workstation, but just configured from a central location, and a lot less likely to work. what i want out of dhcp IS something that is truly dynamic, so that if management decides to change the configuration, then the configuration truly propogates to reflect the changes, and it is not necessary to walk around to each machine and do it manually, as would be the case with static assignment.