dhcp1 at thehobsons.co.uk
Tue May 6 08:46:40 UTC 2008
Eustace, Glen wrote:
>We currently have 4 DHCP servers, 1 at each site + a 2nd at the main
>site. Each site peers with the second server at the main site.
>This provides 2 servers for each network.
>In terms of increasing availablilty, is there anyway of having
>multiple peers ? If not, which I believe is the case, what is
>considered to be best practice for improving availability ?
>Clustering ? sub-dividing sites into more zones each with their own
>Any comments appreciated.
I think you have about the optimum setup there. You can only have two
peers in a failover relationship, so it's not really practical to add
additional servers. To completely lose DHCP service then you'd have
to lose both a site-local server AND the WAN link - at which point
you probably more to worry about than just the DHCP.
As long as you have reasonably reliable servers, and a reasonably
reliable network, then I personally wouldn't be too concerned.
Of course, the other factor is having plans (as part of your business
continuity process) so you know what to do if you do have a failure -
that is far better than lots of redundant servers etc and everyone
running round like headless chickens when a failure still happens ;-)
You could have a 'warm spare' DHCP server fairly easily - just
configure it ready to take over from a live server but with an empty
leases file. Should a server fail, then shut it down and start up
it's replacement, then wait while it copies the leases database over
from the peer. You'll obviously need a WAN link for this to work, but
IMHO a backup (even a 64k ISDN channel or VPN over ADSL) is so easy
and cheap to have that if you are talking about increasing
availability from what you have then you'll already have a redundant
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