Multiple DHCP Servers with DDNS Best Practice/Workaround?

Simon Hobson dhcp1 at
Thu May 12 17:02:01 UTC 2011

Colin Simpson wrote:

>  > 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?

Only reading the last sentence I wrote !

Thinking some more, it may be worth checking the exact update command 
used in the current code. If the deletion is of "any A record 
belonging to <FQDN>" then things will break. On the other hand, it's 
quite possible the deletion command could be to delete a specific A 
record - in which case server A would in fact leave the record alone. 
Having failed to delete the A record, it may well then not try to 
delete the PTR record either. It will however scatter error messages 
throughout the logs.

Simon Hobson

Visit for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
Christmas stocking fillers. Some available as e-books.

More information about the dhcp-users mailing list