Duplicate DHCPACK from a failover pair

Abu Abdulla alhanbali montaqa at gmail.com
Wed Oct 19 06:02:50 UTC 2011


OK i got my answer here:
https://lists.isc.org/mailman/htdig/dhcp-users/2009-July/009478.html

On Tue, Oct 18, 2011 at 1:11 PM, Abu Abdulla alhanbali
<montaqa at gmail.com> wrote:
> Hi,
>
> I am running the server 4.1.1 with failover configured. The clients
> receive DHCPACK from both servers. this causes the client to reboot in
> many cases since it might first receive DHCPACK from a different
> server than the one specified in the DHCPRERQUEST 'server identifier'
> field.
>
> The scenario is as follow:
> - The client is broadcasting DHCPDISCOVER
> - Both servers send DHCPOFFER
> - The client choose one of them (the first one it receives) and
> broadcast DHCPREQUEST including the server that it chooses in the
> 'server identifier'
> - Both servers send DHCPACK which causes the client to reboot if it
> receives the first DHCPACK from the wrong server.
>
> My questions:
>
> - Is it as per the RFC that both servers can respond with DHCPACK. Is
> this what they call ‘lazy’ update. Can we disable it.
> - In RFC 2131 (Figure 3) it shows that one server (should/can?)
> respond. What is the difference between this and the failover draft
> 12. Should the client implement different DHCP firmware based on the
> current DHCP setup (using for example a couple of standalone DHCP
> servers or a failover pair).
>



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