> > => I'm curious about this, does DHCP broadcast its existence to
> > clients that never used it when it comes up? Seems a bit strange
> > to do that. I don't even know how it could speak to a client unsolicited.
> >
> Yes, I do not think there is any message that has currently been defined
> in DHCP, that the servers broadcast without client solicitation.
There are generally two ways to discover the existance of a server:
- broadcast its existance (e.g., via a DHC broadcast or RA "DHC
server present" bit)
- have clients periodically poll the server
Each has different tradeoffs in terms of timeliness of discovering the
server vs. load on the network, etc.
Those assuming a broadcast mechanism is needed may be making the
assumption that if an admin turns on a DHC server, it is a
_requirement_ that all nodes start using DHC effectively
_immediately_.
It is not at all clear to me that this is a requirement.
I.e., it might be just fine to have all clients learn of DHC within
say 1-2 hours (if not longer), in which case background polling is
just fine.
Remember, I don't think we're necessarily talking about the case where
a DHC server goes down. We're presumably talking about the case where
no DHC servers exist (and haven't for a long time), but the admin
decides it's time to enable DHC going forward.
Thomas
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