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

[Darren Ankney]

Assuming the configuration on “server1” is the same excepting “this-server-name”, you don’t seem to have a configuration issue.  

How many clients are going un-acked?  Is this DHCPv4 or DHCPv6?  

The behavior you are expecting is influenced by the 'the values of the “secs” field’ in DHCPv4.  In my experience, many clients fail to increment this value.  If the value is ‘0’ in perpetuity, the server has no way to know that the client has been trying to get a lease for an extended period of time.  You can check this with a packet capture.  The field is in the DHCP header part.

The logs should also tell you how many un-acked clients the server is currently aware of.  I personally haven’t run the load balancing configuration , but running the hot-standby configuration in DHCPv6, I’ve seen these log messages.

Before a client will be added to the ‘un-acked clients’ count, the “secs” field (DHCPv4) or the “elapsed time” option (DHCPv6) (note, I think the DHCPv6 equivalent  might be in milliseconds) will need to evaluate to greater than 10 seconds.

> On Jan 1, 2023, at 7:11 PM, Mathias Aichinger <mathias.aichinger at easysol.at> wrote:
> 
> Hi,
> 
> I currently playing around with the HA and load balancing and I one question appeared:
> 
> Scenario:
> 
> Multiple DHCP-Relays at different sites with both KEA-Servers as DHCP-Servers. Both servers are available and the load balancing shifts the requests between the two servers.
> 
> Incident: Because of a network issue Kea 1 is not available from the clients. The network connection between Kea 1 and Kea 2 still works, so no partner-down state.
> 
> Expected behaviour: Kea 2 sees the unacked clients of Kea 1 and sets Kea 1 in partner-down state and handles all requests.
> 
> Experienced behaviour: Kea 2 still reports HA_BUFFER4_RECEIVE_NOT_FOR_US and does not handle the requests
> 
> Is there a misunderstanding or configuration mistake on my side?
> 
> {
>          "library": "/usr/local/lib/kea//hooks/libdhcp_ha.so",
>          "parameters": {
>            "high-availability": [
>              {
>                "this-server-name": "server2",
>                "mode": "load-balancing",
>                "heartbeat-delay": 10000,
>                "max-response-delay": 60000,
>                "max-ack-delay": 10000,
>                "max-unacked-clients": 1,
>                "delayed-updates-limit": 100,
>                "peers": [
>                  {
>                    "name": "server1",
>                    "url": "http://192.168.248.1:8080/",
>                    "role": "primary",
>                    "auto-failover": true
>                  },
>                  {
>                    "name": "server2",
>                    "url": "http://192.168.248.2:8080/",
>                    "role": "secondary",
>                    "auto-failover": true
>                  }
>                ]
>              }
>            ]
>          }
>        }
> 
> Thank you,
> 
> Mathias
> 
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