DHCP failover doesn't receive DHCP requests in secondary server
robertocarna36 at gmail.com
Wed Aug 15 17:28:23 UTC 2018
Thanks a lot for your help.
2018-08-15 13:19 GMT-03:00 Philippe Maechler <plcmaechler at gmail.com>:
> 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
>> 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.
>> 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.
>> 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.
>> 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>:
>> >> 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>
>> >>> To: "Users of ISC DHCP" <
>> dhcp-users at lists.isc.org>
>> >>> 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: peer dhcp-failover: disconnected
>> >>> Aug 15 11:52:01 dhcp2 dhcpd: 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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