Reducing the value of max-lease-time and default-lease-time

Simon Hobson dhcp1 at
Tue Aug 17 15:36:30 UTC 2010

Mark Krenz wrote:
>I help run the dhcp servers that serve several thousand hosts. I've 
>been considering turning down the max-lease-time and 
>default-lease-time by half their value so that an upcoming migration 
>to another set of DHCP servers will have more flexibility if we need 
>to switch back.
>Is there anything I should be considering before changing these 
>values or should I be ok?  I looked around online for any warnings 
>about doing this but couldn't find anything.  Also, I'd be doing 
>this lease time change a few days in advance of the switchover so it 
>should be plenty of time for all the hosts to pick up the new lease 

As John says, the downside is more activity. Apart from that, it's a 
wise move, and ideally you want to start sufficiently in advance that 
there are no leases (either current or possible) that go beyond your 
planned change date. Eg, if you have max 2 week leases, then cut it 
down to 1 week a fortnight in advance, then down to (say) 2 days a 
week before, and so on.

Of course, if your servers will cope with the load and the network is 
reliable enough, you cold just cut it down to a day, a whole 
fortnight in advance.

Simon Hobson

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