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Jeff
Asked: 2011-04-27 05:34:57 +0800 CST

two DHCP servers on the same network - possible?

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On my network, I have 3 remote sites and one local that all receive DHCP through our central dhcp server.

all the sites have ASAs with dhcprelay and so on.

I have two domain controllers - is it possible to set the second dc as secondary dhcp server, add the information to the ASA - and use it as a failover incase the primary dhcp server is offline?

would this cause problems?

thanks

windows-server-2008 dhcp cisco-asa dhcp-server

2 Answers

  1. Best Answer

    Yes, this is possible and will not cause problems as long as it's configured properly. To setup the second DHCP server as a "failover" you will want to divide up the scopes DHCP 1 is serving. To do this you would configure the same scopes on DHCP 2 as there are on DHCP 1. You would then exclude a percentage of the scope on DHCP 1 and then exclude the opposite percentage of the scope on DHCP 2. This way together they would be serving the full scope.

    Microsoft recommends using an 80% / 20% divide but there is debate on what works best.

    Make sure that if you have any reservations set that they are setup on the secondary DHCP server (if they fall within the scope that will be served from that server). 

             DHCP 1                     DHCP 2

scope    192.168.1.0/24             192.168.1.0/24
exclude  192.168.205 - 254          192.168.1.1 - 204

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  2. Yes, you can do this, probably the easiest way is just to split the ranges.

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