I think he was asking what happens if the servers can't see each other and both start answering clients, possibly creating IP conflicts that must be resolved at some point. Imagine a split fiber ring where the servers can't see each other and the clients on each half of the ring can't see each other. If this persists for a while, duplicate IPs could be allocated. ISC DHCP solved this problem by not allocating addresses that were assigned to the other server unless you hand set "partner down" mode meaning you knew the other server was down and duplicate IPs wouldn't be assigned.
----- Original Message ----- > From: "Chad Catlett" <[email protected]> > To: "David Ramsey" <[email protected]>, "kea-users" > <[email protected]> > Sent: Tuesday, February 8, 2022 6:21:53 PM > Subject: Re: [Kea-users] recover from split brain? > On 2/8/22 14:12, David Ramsey wrote: > > Lab testing I've done shows that the Active/Standby HA configuration > > works well if one or the other DHCP servers fails completely. > > Automatic takeover and recovery work nicely. > > If an Active/Standby HA implementation were to go "split brain" with > > core network severed between DHCP servers, however, both would go > > active and the lease DBs would no longer be in sync. > > How to recover from that when the network is restored? I know there > > are a ton of variables involved - lease times, how long network was > > segmented, # subscribers, etc.... but I am wrestling with what would > > be the optimal approach/logic to consolidate and recover ? > > Help? > > Thanks folks, --David > The admin docs[0] do a fairly decent job of explaining how HA failover > situations are recovered from. The amount of time it takes is directly > related to the dhcp statemachine timers, which are influenced by your > settings. > 0: > https://kea.readthedocs.io/en/kea-2.1.2/arm/hooks.html#scope-transition-in-a-partner-down-case > Chad > -- > Chad Catlett > [email protected] > -- > ISC funds the development of this software with paid support subscriptions. > Contact us at https://www.isc.org/contact/ for more information. > To unsubscribe visit https://lists.isc.org/mailman/listinfo/kea-users. > Kea-users mailing list > [email protected] > https://lists.isc.org/mailman/listinfo/kea-users -- ISC funds the development of this software with paid support subscriptions. Contact us at https://www.isc.org/contact/ for more information. To unsubscribe visit https://lists.isc.org/mailman/listinfo/kea-users. Kea-users mailing list [email protected] https://lists.isc.org/mailman/listinfo/kea-users
