Quick failover question

David Halik dhalik at oit.rutgers.edu
Mon Dec 13 16:20:16 UTC 2010


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,

David Halik
Network Architecture&  Applications
Telecommunications - OIT
Rutgers University

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