[Kea-users] Load-Balancing Network issue between Relay and Kea

[Kevin P. Fleming]

On Wed, Jan 4, 2023, at 13:07, Francis Dupont wrote:
> I leave details to our HA expert but it seems your setup requires an active
> load-balancer:
>  - the path between clients and the first server is broken so this server
>    does not receive queries or clients do not receive responses
>  - the path between the two servers work so for the second server the
>    first server is ok
>  - the path between clients and the second server works so the second
>    server believes queries from first server clients are served by the
>    first server so it does not serve them
>  - the second server has no way to detect the problem as it does not follow
>    responses

How does 'max-unacked-clients' factor into this situation? It's important that our servers are able to notice that their peer servers are not responding to clients in a timely fashion and transition those peers to 'partner-down' so they will start serving the peer's clients.

If 'max-unacked-clients' isn't sufficient to address this, then this leaves a fairly large opening in the Kea high-availability story, as any network disruption which causes a server to no longer receive discovery packets from clients, but otherwise receives all expected network traffic, won't be noticed except by the clients! This concerns me, as (like other users here) my Kea servers receive all client traffic via DHCP relays, and misconfiguration of the relay such that it only relays to one server and not both will result in half of my clients not getting DHCP service at all.