samba - May 2020 - Fwd: DHCP Updates to DNS - Multiple Entries with Same IP

On 21/05/2020 21:04, Matt Savin wrote:
> I think you can continue to use '128' (good for load balancing, 
> otherwise 255 is fine). I had the same issue, following dhcpd.conf 
> entries fixed it (the last entry is important):
>
> one-lease-per-client? true;
> deny ? ? ? ? ? ? ? ? ? ? ? ?? duplicates;
> ignore-client-uids ? ?? true;
>
> And it's not a bug, it's by design as is **REQUIRED** by the RFCs.
Perhaps 'bug' was the wrong word ;-)

It is my understanding that with '128', both dhcp servers listen and 
reply to requests, with '255' only one server listens and replies.

Rowland

Rowland,

You're absolutely right - with '128' both DHCP servers listen and
*may*
reply, therefore besides failover provide load balancing. Even if both
servers respond with *Offers* to the client, the client will select one and
issue *one Request* to the selected server.
E.g., below is a log records from my failover DHCP (192.168.0.2) server:
May 17 00:09:37 s-dhcpd-2 dhcpd[1578]: DHCPDISCOVER from 80:77:30:a3:d3:e2
via enp2s0
May 17 00:09:38 s-dhcpd-2 dhcpd[1578]: DHCPOFFER on 192.168.0.173 to
80:77:30:a3:d3:e2 (d-host-2) via enp2s0
May 17 00:09:38 s-dhcpd-2 dhcpd[1578]: DHCPREQUEST for 192.168.0.173
(192.168.0.2) from 80:77:30:a3:d3:e2 (d-host-2) via enp2s0
May 17 00:09:38 s-dhcpd-2 dhcpd[1578]: DHCPACK on 192.168.0.173 to
80:77:30:a3:d3:e2 (d-host-2) via enp2s0

Here's a log record from my primary DHCP (192.168.0.1) server:
May 17 00:09:37 s-dhcpd-1 dhcpd[1565]: DHCPDISCOVER from 80:77:30:a3:d3:e2
via eno2: load balance to peer dhcp-failover
May 17 00:09:38 s-dhcpd-1 dhcpd[1565]: DHCPREQUEST for 192.168.0.173
(192.168.0.2) from 80:77:30:a3:d3:e2 via eno2: lease owned by peer

The ISC DHCP server provides a scheduled mechanism to analyze the available
IP addresses on both servers to maintain balance among them. The analysis
itself compares the number of free addresses on a given server against
those on its peer and identifies variances from a 50/50 split.

Following lines in dhcpd.conf should get rid of duplicates and preserve
load balance with '128':
one-lease-per-client  true;
deny                          duplicates;
ignore-client-uids      true;

Of course, nothing wrong with setting the split to 255 and going to pure
failover.

Thank you for your outstanding Samba community service,
Matt

On Thu, May 21, 2020 at 4:37 PM Rowland penny via samba <
samba at lists.samba.org> wrote:
> On 21/05/2020 21:04, Matt Savin wrote:
> > I think you can continue to use '128' (good for load
balancing,
> > otherwise 255 is fine). I had the same issue, following dhcpd.conf
> > entries fixed it (the last entry is important):
> >
> > one-lease-per-client  true;
> > deny                          duplicates;
> > ignore-client-uids      true;
> >
> > And it's not a bug, it's by design as is **REQUIRED** by the
RFCs.
> Perhaps 'bug' was the wrong word ;-)
>
> It is my understanding that with '128', both dhcp servers listen
and
> reply to requests, with '255' only one server listens and replies.
>
> Rowland
>
>
>
> --
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Mandi! Matt Savin via samba
  In chel di` si favelave...

A bit OT but...
> Following lines in dhcpd.conf should get rid of duplicates and preserve
> load balance with '128':
> one-lease-per-client  true;
> deny                          duplicates;
> ignore-client-uids      true;
Interesting. But whan happen if a client have a double wired/wireless
network connection, and flip between them?
Reading manpage, get the same address, right?

What happen if two computer with the same name get connected to the
same network?
Still seems to me that get the same address.


Anyway, interesting...

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