Quick failover question

Chris Buxton chris.p.buxton at gmail.com
Mon Dec 13 17:38:47 UTC 2010

With failover, only one of the two servers should respond to a request. They work it out based on a hash of the MAC address, as I recall.

Without failover, e.g. with what Microsoft calls a split scope, you would have the problem you mentioned - two responses, first received wins. But with failover, you won't have that problem.

Chris Buxton
BlueCat Networks

On Dec 13, 2010, at 8:20 AM, David Halik wrote:

> Hello,
> We're currently running 3.1-ESV in support of our VOIP phone system and I'm looking at setting up failover for redundancy. I think I have a pretty good grasp of how everything works, but there is one issue that I haven't been able to find a concrete answer on.
> When a DHCPDISCOVER goes out on the wire from one of the clients, how is it determined whether the primary or secondary DHCP server responds? Is it random? Do they both respond? Do they work it out amongst themselves? I read in the changelog that "Dynamic BOOTP leases are now load balanced in failover", but this doesn't tell me anything about how the process actually happens.
> The reason I'm asking is that we've had an issue with buggy clients where they do not handle receiving multiple responses very well. If it's only ever the primary or secondary responding at one time, then all should work as planned. If both respond and it's a "first one wins" situation, then I won't be able to use failover with these clients.
> Any help would be appreciated, thanks,
> -Dave
> -- 
> ====================
> David Halik
> Network Architecture&  Applications
> Telecommunications - OIT
> Rutgers University
> 732-445-7530
> ====================
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