On Tue, Oct 01, 2024 at 12:34:31PM +0300, Kapetanakis Giannis wrote: > > On 01/10/2024 08:36, Otto Moerbeek wrote: > > On Mon, Sep 30, 2024 at 10:50:06PM +0300, Kapetanakis Giannis wrote: > > > >> How did you solve the problem of initial sync? > >> > >> Suppose one server goes down for maintenance. When it comes up it does not > >> know what new leases have been given by the other server which was all the > >> time up. > >> > >> There are chances that later it gives an IP already given by the other dhcp > >> server. The leases (while down) were not synced. > >> > >> I don't think there is an option for initial sync (like pfsync) and even if > >> you scp the lease file you can't be 100% sure since you might miss > >> something > >> while copying and starting service. > >> > >> This is the primary reason I've sticked with isc-dhcpd and failover peer. > >> > >> G > >> > > IIRC on dhcpd statup all leases from the lease db are advertized to > > the other dhcpds. > > > > -Otto > > Didn't know about this but I don't think it solves the problem. > The starting server is behind and missing entries from the lease file. > > Does the starting server also request a full lease advertisement from the > other server? > > What happens with the other server (which is NOT restarting) and how will it > notify the starting server that there are new leases (without a restart)? > > Unless a server startup triggers full advertizement on all sides. > > G >
Look in src/usr.sbin/dhcpd/sync.c, on receiving a lease, dhcpd checks if the other deamon has old info: /* * our partner sent us a lease * that is older than what we have, * so re-educate them with what we * know is newer. */ So if the starting dhcpd daemon sends out info that is known to be outdated, it wil be corrected by the others. I'm not 100% sure that will cover all cases though. -Otto