Karl Auer wrote: >> They're trivial once you're storing leases in a transactional database. > > With all due respect, Arran, no, they are not. > > Two DHCP servers in a failover relationship must communicate with each > other, each maintaining information about the state of leases that the > other has.
There's a miscommunication here. Arran is talking about two servers sharing a common view of their leases, and synchronizing that view with each other, to maintain a consistent response to client machines. You're talking about the ISC fail-over protocol. The two views just don't meet. > If they do so via a shared database (which seems to be what > you are suggesting, apologies if not) then the entire point of failover > is lost. And that is quite apart from the carefully timed state > management that must occur during takeover or recovery in the case where > a server drops out, is not reachable by its peer or is deliberately > taken offline. Not to mention the possibility of having several servers > participating in various failover relationships. I disagree. Really. I spent most of a year working with DHCP in a previous life. Your comment is "correct", where the word "correct" has connotations of "theoretical analysis that conveniently ignores real-world situations". Like losing the entire d*mned lease database. Or working in settings like (1) enterprises, where 99.99% of lease renewals are for the same MAC/IP setting, or broadband/dial-up ISP's, who have interest in *not* handing out the same IP to the same MAC for any period of time, > No - not trivial. 90% of the situations are trivial to handle. The other 10% can go buy a $500,000 solution. The people selling the $500K solution are welcome to the support nightmare. > Hence my interest in how freeradius will be doing all this. It will do it *very* well, or not at all. Alan DeKok. - List info/subscribe/unsubscribe? See http://www.freeradius.org/list/users.html