setting a priority between redundant dhcp servers?

Simon Hobson dhcp1 at thehobsons.co.uk
Tue Jun 3 06:50:32 UTC 2008


Louis-David Mitterrand wrote:

>Is there a way to set a priority between two dhcp servers operating on
>the same LAN?
>
>I've noticed that my intended "secondary" answers more readily then the
>(better spec'ed) "primary". Is there a reason why one server replies
>faster than another identically-configured one?

What other services are the servers running ? How much network 
traffic are the handling ? Did you once run with one server only and 
then add the second - if so, which way round ?

Typically, clients will accept the first offer they receive, so all 
it needs is a difference of probably only nanoseconds in response 
time to deiced which response packet gets on the wire first. If one 
server is also handling other traffic, then that will mean the DHCP 
packets will have a slight delay before they get out.

Also, if you ran one server for a while, then clients may well have 
gained an affinity for it (they will normally try to renew with the 
server that issued their lease). So if you "secondary" server was 
once the only one, then clients will continue to use it in preference 
to the newer one.


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