How do I configure Windows XP to choose between one of as two DHCP servers in one (same) LAN?
If you've got two (2) DHCP server computers in the same layer 2 broadcast domain, clients are going to be (mostly) randomly assigned addresses by either server computer. The one that answer's the client's DHCPDISCOVER reuqest first is going to end up assigning the address to the client.
I'm not sure this is a great idea. You're adding what is, essentially, a non-deterministic element to your network. If you want redundancy in DHCP, consider using a program to monitor the "health" of the primary DHCP server and, in the event of failure, bring up the secondary DHCP server.
Please see the existing question that directly answers this issue
These are not client side changes
I am not aware of any way to specify a DHCP server from a network client. My question to you would be - why would you want to? In an AD, you can have multiple redundant DHCP servers, and you can configure them to manage the same scope without overlapping addresses. You can also configure reservations and several other things. If you need to have different DNS or WINS servers for some reason, the machines that require the exceptions can have manually configured DNS or WINS entries but still use DHCP.
I don't think it is really recommended to have two DHCP servers on one lan...
If it is for redundancy one option is to use cluster services so that the dhcp files are stored and referenced by which ever server is running the dhcp service.
another solution would be to put you separate lans in vlans or similar so that only the client that are on that lan with each dhcp service will receive the correct dhcp request
hope that helps
I think that it should be perfectly valid to have more than one DHCP server on the same LAN. In our case we want it because we have two gateways and we want all the settings to be received automatically by the clients but have some clients utilizing one gateway and some the other gateway (due to different characteristics of the network beyond the gateway).
As is mentioned in another thread, a server-ranking solution was proposed in 1997 (see http://tools.ietf.org/html/draft-ietf-dhc-sso-00) but does not seem to have been implemented.
It should be perfectly possible for client utilities to provide a selection, based on DHCP server host name or IP address. Clients receive a DHCPOFFER from all DHCP servers that respond to a DHCPBROADCAST, and then the client sends a DHCPREQUEST. These DHCPREQUESTs could be filtered according to pre-established rules, with a fall-back of responding to the first DHCPOFFER receieved if no DHCP server passes the filter.
In fact, I have seen a number of occasions where problems have been caused on small networks by installation of a second DHCP server (the default configuration of all ADSL routers, for example). Client rules for filtering could prevent these problems.
Sounds like you're trying to load-balance your gateways by evenly assigning them to routers via DHCP.
Really the optimum solution is to do the load balancing on the gateway device itself. Your LAN should only have one gateway, and that gateway device should have three interfaces, an "inside" one connected to your LAN, and two "outside" ones connected to your two external gateways.
You can then flexibly configure things as you need on the gateway device without having to involve any individual machines on the LAN.