Failover static and dynamic lease

[Simon Hobson]

Marcos Renato da Silva Junior <marcosjr at dee.feis.unesp.br> wrote:

> I have a server with static lease (some hosts) and dynamic lease (range 192.168.0.100 192.168.0.110;).
> 
> I want to add a second server for redundancy. Whats the better way? Configure failover? or just keep identical copies from the dhcpd.conf filein both servers?

For the static assignments (I assume host statements with fixed-address statement), it's sufficient to just duplicate the config on both servers.

For dynamic ranges you have choices.
"Failover" is one approach. With some caveats in terms of managing state, this allows one or other server to carry on if it's partner fails - leaving all clients with the same address.
If you have enough addresses, and don't mind hosts changing address if a server fails, then you can just configure two (or more if you want) servers with non-overlapping ranges. If a server fails, then clients will be unable to renew leases and will eventually get a new lease (different address) from another server. For this to work, you need enough addresses that if a server fails, the other server(s) have enough addresses to service all the clients.