Option 50 in failover mode
Simon Hobson
dhcp1 at thehobsons.co.uk
Mon Nov 28 06:56:05 UTC 2011
I wrote:
>Bear in mind that if you rely on each server having a separate pool
>capable of serving the network (which incidentally is NOT failover),
>then in the event of a server failing, all the clients using that
>server will get new addresses which may or may not cause problems.
And your Dynamic DNS updates **WILL** break - that is guaranteed.
Client gets lease from server A
A gives out a lease and updates DNS with clients hostname & IP address.
B now dies.
Client carries on, and after a while attempts to renew it's lease. A
doesn't respond, so eventually client braadcasts to find another
server. B now responds.
B gives client a different address - so client changes address and
all it's open sessions get broken.
B attempts to update DNS - but there are A and PTR records put there
by A. B will **NOT** perform the update as it recognises that the
entries currently in there are not "owned" by itself.
Client now has different IP address, but DNS entries point to old
address. This will not change until A is brought back online, expires
it's old leases, cleans up the DNS, AND the client renews again with
B.
--
Simon Hobson
Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
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