[Dnsmasq-discuss] Making dnsmasq make OFFER faster than virtualbox NAT DHCP
simon at thekelleys.org.uk
Mon Jan 23 18:27:11 GMT 2017
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On 23/01/17 17:45, wkitty42 at gmail.com wrote:
> On 01/23/2017 06:49 AM, Simon Kelley wrote:
>> Actually, it's permitted to have more than once DHCP server, but
>> the client is entitled to wait for some time to hear from them
>> all, and then pick whichever one it prefers,
> that's interesting... i can't say that i've ever heard that
> before... maybe it has been corporate policy on all the networks
> i've dealt with over the years?
> it is something that i may do more research on because i don't want
> to pass bad information as i have apparently just done... do you
> have any pointers to documentation on this aspect of DHCP servers?
>> so trying to implement server priority by speed-of-reply is
>> doomed to failure.
> yup! seems to be that way :)
> thanks for the clarification!
To be honest, I've never seen it used, except possibly in
high-availability fail-over scenarios, nevertheless it's in the spec:
see RFC-2131 para 4.4.1 Initialization and allocation of network address
"The client collects DHCPOFFER messages over a period of time, selects
one DHCPOFFER message from the (possibly many) incoming DHCPOFFER
messages (e.g., the first DHCPOFFER message or the DHCPOFFER message
from the previously used server) and extracts the server address from
the 'server identifier' option in the DHCPOFFER message. The time
over which the client collects messages and the mechanism used to
select one DHCPOFFER are implementation dependent."
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