Tuesday, October 01, 2024

Re: dhcpd with failover

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

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