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I have 2 DHCP servers and the client will take the first offer but I want to see the request and the decline for the 2 servers.

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Your question is unclear. When you say you want to "see" the request and the decline, do you mean with something like Wireshark? –  Robin Green Apr 16 '11 at 6:52
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What is the actual problem you're trying to solve here? Your question title and your actual question are different. –  RobM Apr 16 '11 at 7:13

2 Answers 2

It's common to have the routers for each subnet have the broadcast forwarding command in a different order. Half the routers will forwward to DHCP server 1 first and the other other half will forward to DHCP server 2 first, thus achieving a crude, but effective, load balancing.

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If your DHCP servers are not sharing a common scope database (ISC dhcpd is capable of doing that, the Windows Server DHCP server implementations are not), you will need to set up your scopes in a way so that they will serve addresses from different ranges - e.g. dhcp1 would only serve 192.168.0.21 - 192.168.0.80 while dhcp2 would serve 192.168.0.81 - 192.168.0.160.

Microsoft is advocating an 80/20 share in its documentation for several decades now, although there never has been a precise explanation on the exact nature of these numbers. The implicit assumption here is that in the case of an outage of the primary DHCP server, you will be able to bring it back online before your smaller 20% scope is going to fill up - which obviously will not work for some scenarios.

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I've been using a (close to) 50/50 split forever and it works great. If you have a DHCP server that is clearly "faster" than the other, I'd use 80/20 because the one will be handing out more addresses than the other. –  Chris S Apr 16 '11 at 14:39
    
We do the same as Chris - a 50/50 split. I've found this works very well in practice, and with Windows 2008 r2 they still haven't got the DHCP servers sharing/exchanging IP info, but at least they have added the ability to create a scope that's split between servers to the scope creation tools... –  RobM Apr 16 '11 at 17:57

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