dhcp failover

Simon Hobson dhcp1 at thehobsons.co.uk
Wed Jul 5 09:52:19 UTC 2006

Olivier Nicole wrote:

>  > ISC DHCPD makes ping checks to detect ip availability. If you loose your
>>  lease file, I think it is not so bad, because the second dhcp server will
>>  detect that the IP that it wants to give is not free.

>Except that many windows firewall will not let the ping get through,
>so it will not detect that the IP is already in use.
>A ping reply means that the IP is in use, but no reply means nothing...

Not only that, but a ping reply means that the address is marked ABANDONED.

If the device using that address goes away (perhaps it's a visiting 
laptop) then that address will never be reused until you run out of 
addresses to the administrator manually deletes it.

So :

No ping reply = doesn't mean anything, it could be blocked by a firewall

Ping reply = abandoned address which is not good.


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