DHCP failover doesn't receive DHCP requests in secondary server

[Philippe Maechler]

iirc with the latest patch, only the primary server replies to clients when
the split value is set to 255

Gregory Sloop <gregs at sloop.net> schrieb am Mi., 15. Aug. 2018, 18:16:

> Top posting:
>
> I think the term "fail over" causes some confusion.
> DHCPd in "fail-over" isn't what I'd typically think of, when I think "fail
> over."
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> When I think fail-over, I think of a server that essentially does no
> active "work" while the primary is up and functioning - other than *getting
> ready* to handle the load of the primary when it goes down.
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> Yet DHCPd fail-over is really *load-balancing* [at least in "normal"
> setups] with a bunch of communication between the two to handle the
> failure/unavailability of *either* server.
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> Thus, in regular practice, both servers are seeing requests and answering
> them, and [again in "normal" setups] will have approximately half of the
> leases distributed to each server.
>
> HTH
> -Greg
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> *RC> Dear, thanks for your response...So I will review the DHCP agent as
> you said. RC> But now I have a question: RC> If both DHCP servers always
> receive DHCPREQUEST packets, does it mean RC> that in normal condition
> (primary and secondary server are running UP) RC> both DHCP servers
> responds these requests ??? Or only the primary RC> server responds the
> requests in despite of the secondary server is UP RC> too ??? RC> Thanks a
> lot again, regards !!! RC> 2018-08-15 12:38 GMT-03:00 perl-list <*
> perl-list at network1.net*>:*
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> * >> The problem isn't with the secondary server.  The DHCP packets must
> always go to both servers.  If the packets are relayed from a relay agent,
> then the relay agent must be configured to send to both of the DHCP servers
> (On a Cisco router, that would involve having ip helper-address listed
> twice, for example). >> If no relay, then the DHCP servers must both be on
> the same LAN with the clients. >> When both of the primary and secondary
> servers are running, you should see logs of the DHCP packets in both
> servers logs. >> ----- Original Message ----- >>> From: "Roberto Carna" <*
> robertocarna36 at gmail.com*>*
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> * >>> To: "Users of ISC DHCP" <*
> dhcp-users at lists.isc.org*>*
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> * >>> Sent: Wednesday, August 15, 2018 11:06:08 AM >>> Subject: DHCP
> failover doesn't receive DHCP requests in secondary server >>> Dear people,
> >>> I´ve implemented a failover scheme with ISC-DHCP-SERVER in two >>>
> different servers, with the same version of the package and OS. >>>
> Everything seems to be OK, but when a execute "service isc-dhcp-server >>>
> stop" in the primary server, in the secondary server I can see: >>> Aug 15
> 11:52:01 dhcp2 dhcpd[5839]: peer dhcp-failover: disconnected >>> Aug 15
> 11:52:01 dhcp2 dhcpd[5839]: failover peer dhcp-failover: I move >>> from
> normal to communications-interrupted >>> what is correct, but after that
> the secondary server doesnt' receive >>> any DHCPREQUEST packet from
> clients. >>> So, my faoilover scheme doesn't work, because if primary
> server goes >>> down, the secondary server doesn't receive any IP request
> from >>> clients. When I start the isc-dhcp-server on primary server, at
> this >>> moment I can see the DHCPREQUEST from clients to primary server.
> >>> What can be the problem with the secondary server please ??? >>> Thanks
> a lot!!! *
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