server changing options dynamically

Brian Johnson voyager.106 at
Wed Feb 18 20:51:07 UTC 2009

Hello all,

This question is actually interesting to me and I'm surprised I stumbled on
it so recently. We're currently in the midst of moving to a new set of DNS
servers at work. I've gone through and made the appropriate changes in the
DHCP server to reflect the new servers and have made sure the old servers
are not referenced anywhere. The maximum lease time we have on any subnet is
1 day, with some as low as 30 min (wireless network in particular). However,
2 weeks after we've made the change, we're still seeing wireless users and
others hitting the old servers. My theory (without finding anything to
confirm/refute) is that machines left on will only renew their ip lease but
will not receive changes to "option domain-name-servers". If there is online
docs that discuss this issue, can somone please point me to it (I've tried
with Google(tm) but have not had any luck with my queries) and, if possible,
a way to get clients to take the new option.


Brian Johnson

On Tue, Feb 17, 2009 at 7:05 PM, <sandeep.vashisht at> wrote:

>  Hi All,
> Is it possible for an server to change the network parameters at the
> renewal time.
> I am trying to find out the desired server behaviour in some document but
> could not get it.
> If the DNS/FTp or any other parameter is changed on the fly in server,
> then what the client is supposed to get which is already linked and is
> asking for a renewal.
> I guess if the IP address is changed then the server should send the NAK.
> what about the parameters other than IP address.
> I have seen some of the cllient which update the values only at the
> discover time and then just keep on renewing the lease without updating all
> the parameters.
> is there any RFC that talk about the servers/client behaviour?
> Thanks,
> S.V.
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Brian Johnson
"And I will be even more undignified than this, and will be humble in my own
sight." (2 Samuel 6:22)
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