Multiple DHCP Servers with DDNS Best Practice/Workaround?
Colin.Simpson at iongeo.com
Thu May 12 16:12:28 UTC 2011
On Thu, 2011-05-12 at 16:30 +0100, Simon Hobson wrote:
> Yes you would. Take this simple timeline :
> Server A issues lease and adds DNS entries
> Client move to another network
> Server B issues lease and updates DNS
> Lease at server A expires, server A removes DNS entries.
> Client now has no DNS entries, and Server B will not add them again
> as it's lease record shows that it's already added them. Client will
> be without DNS entries until it either moves to another network (so
> Server C can add them), or it's lease expires with server B and it
> then rejoins the network. In the former case the client will get DNS
> entries, but only until it's lease at server B expires and they get
> removed again.
> To avoid this you would either need to prevent deletion of the DNS
> entries (in which case you'd need to come up with some means of
> garbage collection), or modify the code to not delete entries if the
> A record doesn't match what the server thinks it added. The latter
> would probably work, but it's more code hacking.
Surely Server B can happily replace the DNS entry placed there by server
A. Then when Server A expires the original lease it should realise that
the DNS entry (the A record for the client) wasn't the one it put in
there (i.e doesn't match the IP in the A record doesn't match it's
leases file) and should leave it alone? It should still remove the
reverse PTR record to keep things tidy.
So no communication should be necessary.
Or am I missing something?
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