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</o:shapelayout></xml><![endif]--></head><body lang=DE-CH link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:DE-CH'>hello kea users<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:DE-CH'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:DE-CH'>I’m once again looking for a way to make our dhcp setup more stable. Currently we use the isc dhcpd without failover. For each active dhcp server, there is an inactive one (cold standby?), which gets the configuration and lease file every few minutes. If something breaks, we have to manually take the broken server offline and activate the second one. This setup worked more or less stable for more than 10 years.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:DE-CH'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:DE-CH'>But still this setup has it’s disadvantages that I’d like to get rid of. Of we have a maintenance window and have to take the router, where the active server is connected to down, we don’t have a running dhcp setup. New clients won’t be able to get a lease and existing clients fail to renew their lease. <o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:DE-CH'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:DE-CH'>From the kea-user-guid (</span><span lang=EN-GB style='mso-fareast-language:DE-CH'><a href="https://kea.isc.org/docs/kea-guide.html#high-availability-library">https://kea.isc.org/docs/kea-guide.html#high-availability-library</a></span><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:DE-CH'>)<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:DE-CH'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:DE-CH'>The Kea HA hook library supports two configurations also known as HA modes: <b>load balancing</b> and <b>hot standby</b>…<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:DE-CH'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:DE-CH'>In the <b>load balancing</b> mode…<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:DE-CH'>When one of the servers allocates a lease for a client, it notifies the partner server over the control channel (RESTful API), so as the partner can save the lease information in its own database. <b>If the communication with the partner is unsuccessful, the DHCP query is dropped and the response is not returned to the DHCP client</b>. If the lease update is successful, the response is returned to the DHCP client by the server which has allocated the lease.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:DE-CH'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:DE-CH'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:DE-CH'>In the <b>hot standby</b> configuration…<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:DE-CH'>The secodary server receives lease updates from the primary over the control channel…<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:DE-CH'>When the secondary server detects the failure of the primary, it starts responding to all DHCP queries.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:DE-CH'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:DE-CH'>My question is:<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:DE-CH'>In the load balancing mode, when one server dies, both servers won’t hand out leases, because the notification over the control channel fails, right?. If so, where is the HA part in here?<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:DE-CH'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:DE-CH'>In a hot standby configuration, what happens when the lease update fails? Will the “primary” server hand out the lease or not?<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:DE-CH'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:DE-CH'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:DE-CH'>Prior to 1.4 there were several messages on this list about a setup with multiple (two) kea instances accessing both the same database (cluster). Is such a setup supported/recommended or not? I guess not, because the initial text on the above url states, that “supports two configurations also known as HA modes”<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:DE-CH'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:DE-CH'>Best regards<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:DE-CH'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:DE-CH'>Philippe<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial",sans-serif'><o:p> </o:p></span></p></div></body></html>