if possible to make dhcp as active/backup method

[Simon Hobson]

Julie Xu <xll40 at hotmail.com> wrote:
> currently my dhcp servers are failover, but, for some reason, the both server has to be online, any of them off line cause IP address renew delay, even equipment offline for a while.

Part of that is by design.
Are you aware that if you take one server of a failover pair down then you must also tell the other one that the partner is down ? If you do this then the active server will take over the whole range and serve up addresses. If you don't do this, then complications arise (I don't recall the details as I don't use failover myself).

The reason the active server doesn't automatically go into partner down state is that there are a number of scenarios where the partner could be online and active - it's just that inter-server traffic is broken/blocked. I believe in the latest versions there is a config option to allow for "auto partner down".