failover and loadbalance for relayed requests

[Sean McMurray]

On 06/03/2015 07:48 AM, Leandro wrote:
> Hi dhcp users:
> I have a few years working with isc dhcp, I would like to move my dhcp 
> service scheme to a virtualized enviroment to provide HA and load 
> balance on a relayed scheme.
> I would like to ask for some documentation to read and also ask for 
> the dhcp isc failover capabilities and recommendations.
> I imagine to setup two servers for instance with lease database sync 
> and two ips configured on the relays ... is that possible ? how does 
> iscp manage the leases db sync?
ISC DHCP can only do 2 coupled servers. If you are looking for more 
redundancy/load balancing than that, you will have to be creative.
For instance, if you are just looking for load balancing, you could put 
your leases file on a clustered filesystem and have multiple servers 
serve different pools in the same subnet, using the same leasefile. But 
solutions like that are outside of the box.

For built-in failover functionality in ISC dhcpd, you configure two 
servers to know about each other. You define which pools they share and 
what the split is. For example, you could have the primary serve 2/3 of 
the pool, and have the secondary serve 1/3. The two servers communicate 
back and forth about what leases they have served. When one fails, the 
other takes over and eventually recovers the other's leases.