Guest Alex Posted September 24, 2007 Posted September 24, 2007 I have taken over a network with ~150 servers (Mixed Windows 2000 & 2003) and 50~workstations (Mixed Windows 2000 and XP) with all servers and workstations running on static IP addresses. The network is spread across a number of VLANs and everything is running without problem, but we have recently had to change our primary and secondary DNS servers which resulted in a large amount of manual work on every box. Subsequently we would like to look at deploying a redundant DHCP configuration with reservations for all of the servers and probably all of the clients as well, but are struggling on the best way to achieve this. If we were to deploy two DHCP servers with either a 50/50 or 80/20 share of each subnet can anyone clarify how reservations are used. For example using the settings below can anyone confirm if DHCP Server 1 were to fail, would DHCP Server 2 hand-out the reserved addresses to Server 1, 2 and 3 even though those addresses are actually part of DHCP Server 2's exclusion list ? Can anyone suggest a better method we should consider to achieve a redundant dhcp deployment ? Thanks, Alex. DHCP Server 1: 192.168.1.11 - 192.168.1.250 Exclusion: 192.168.1.119 - 192.168.1.250 Reservations: server 1 - 192.168.1.11 server 2 - 192.168.1.12 server 3 - 192.168.1.13 DHCP Server 2: 192.168.1.11 - 192.168.1.250 Exclusion: 192.168.1.11 - 192.168.1.118 Reservations: server 1 - 192.168.1.11 server 2 - 192.168.1.12 server 3 - 192.168.1.13 VLans in use: 192.168.1.0 192.168.2.0 ...... 192.168.14.0
Guest ObiWan [MVP] Posted September 24, 2007 Posted September 24, 2007 Re: Advice on redundant DHCP Server configuration with reservations <snippage> > Can anyone suggest a better method we should > consider to achieve a redundant dhcp deployment ? I'd use subnetting and routing in addition to VLANs; what I mean is that you may setup your server so that they'll be sitting on a different subnet and reachable through a router at this point you'll have a full subnet for your server and a full range (w/o any need for reservations) for your clients going back to DHCP fault-tolerance; the usual approach is to setup things using the 80/20 principle, that is, having a subnet with N addresses, you throw away the reserved ones and then assing the remaining ones so that one DHCP server will serve the 80% of the remaining addresses and the other will serve the other 20% .. but.. there's another approach too that is .. the 100/100 :) no, I'm not kidding :D although the idea can't always be applied, is some cases it's feasible and will allow you to always have your network fully served the idea is to change the netmask of the DHCP subnet so that you'll have TWO times the addresses you need, at this point you may split those addresses amongst two DHCP servers each server will so give out 50% of the whole subnet, but since even the 50% of the subnet will cover the 100% of the needed IPs, your network will still be FULLY covered; then if you want to make things more complex and add some more tolerance you may even use FOUR DHCP servers and set then up to use the 80/20 rule on each half of the subnet HTH -- * ObiWan Microsoft MVP: Windows Server - Networking http://www.microsoft.com/communities/MVP/MVP.mspx http://italy.mvps.org
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