Where best to place DHCP

Let the DHCP continue to run on the single Windows 2003 server and create multiple DHCP scopes.. Enable DHCP relay from the various routers into each IP address subnet with the "ip forward-protocol" command on the subnet facing interface. Now you only have to take care of one DHCP server, not multiple DHCP servers or multiple DHCP relay servers. Each router could act as a DHCP server for its connected subnets, but the Windows 2003 server offers better visibility into the use of the address scope and easier changes to reservations and scope options.

----- Scott Perry Indianapolis, IN

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It's important to know how many sites we're talking as, one server in a fairly large environment could also be a single point of failure. You may need to split up the load on several servers to develop a more fortified plan. It's important though in a windows network to let DHCP and DNS co-exist on the Win2k3 boxes. It will facilitate both processes if you do for a variety of reasons, namely dynamic dns, especially if you're not running WINS.

DHCP is not one of those things that when it goes down your network is down. You have DAYS to get a broken DHCP server up and running before it will be a significant problem. Workstations renew their lease after half the lease time has expired, so if you have a 14 day lease, the workstation will renew the IP address after 7 days. When a Windows workstation reboots, if the DHCP server is unavailable it will use the last address (and DHCP options) that it last received, iff the lease is not expired.

It is always better to centralize services like DHCP because if you need to change any of your DHCP options, you have only one place to change them. If you want to be able to see what addresses are in use on a particular switch, enable DHCP snooping on the switch. The bigger your network, the more uniform and simpler you want your network.

If you want redundant DHCP services without having to use split scopes, their are several vendors that have redundant DHCP server products.

As always the size/complexity of your network(s) is important. The answers you've received are excellent. I just want to underscore and add our experience.

We are a strongly M$ AD shop in a modest network. There are 51 sites, mostly fiber and 18 T1, with about 2500 hosts. There are two DHCP servers that serve all subnets. We split each scope between the servers. (this doesn't really "balance" the load, it is interesting to observe the distribution of leases, though). Unless your network is changing all of the time, once this is set up, there is only a modicum of effort needed to maintain--new scopes, reservations, etc.

I highly recommend using the Microsoft DHCP and integrate DNS servers with your domain controllers. If your workstations are mostly XP or (shudder) Vista, this will be very successful. We use 60-day leases and it is very stable. DDNS settings should be used.

Also, if you haven't already done so, study and move to direct hosting of SMBs over TCP rather than using NetBT. We haven't completely eliminated the WINS servers, yet, but it is a much cleaner and more straightforward (said with irony...) way to connect to server resources.

It is worth the time investment to dig deeply into Microsoft's documentation to understand its use of ip and protocols.

good luck.

placed the DHCP server on the switch controlling that subnet. I have preferred it there because if the server goes down (which does not happen often), then DHCP is not affected. I also consider DHCP more of a network function that a server function. I have personnel here putting up the argument that it would be best to place the DHCP on our Win/3k servers and if necessary use DHCP relay either on servers on that subnet or in the router.

generally have designed/laidout networks keeping them simple and allowing an item to function in the manner it was designed to. What I am saying I try to keep networking functions on networking devices allowing my servers to function serving the requests of users.

here now that insist on having DHCP on the servers. Particularly since Win/3k DHCP can talk to the integrated-DNS server. Just wanted to "hear" from others on their view of this matter.

Thrill5 explained it very well. Nevertheless i prefer running DHCP service on routers because of their stability advantages and their centralized placements.