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    kea dhcp server in HA mode drops 50% of dhcp requests

    Scheduled Pinned Locked Moved DHCP and DNS
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    • T
      thomas.hohm
      last edited by thomas.hohm

      Hi,

      we are experiencing issues with dropped dhcp packages when using kea dhcp in high availability setting.
      We found a lot of wifi devices having problems to get ip addresses via dhcp.

      Our setup:

      • pfSense 24.11 on netgate appliance with Super Micro 1537, Intel(R) Xeon(R) CPU D-1537 @ 1.70GHz, 32 GB RAM, 450 GB SSD
      • LAN: pfSense cluster and clients: 10 Gbps fiber
      • HA sync LAN: 1 Gbps copper (officially support nic card, not the onboard nic)
      • pfSense cluster running captive portal, dhcp, dns, firewall services

      Test performance of dhcp server with perfdhcp on an ubuntu client:
      perfdhcp -l <local LAN IP on client> -d 5 -r 10 -R 10 -n 500 <pfsense active cluster member>
      (10 dhcp requests per second, 500 requests in one set of tests).

      Result:
      Phase Discover-Offer:

      • 500 discover packets sent
      • 257 offers received by client
        (packet capture on pfsense LAN interface and on client LAN interface confirms this figures)
      • min delay: 93 ms
      • avg delay: 300 ms
      • max delay: 646 ms

      Phase Request-Ack:

      • 257 request packets sent
      • 98 ACK packets reveived
      • min delay: 266 ms
      • avg delay: 544 ms
      • max delay: 900 ms

      Investigations during the tests did not show any bottleneck (at least for me):

      • ping between client and pfsense active cluster member: 0.2 - 0.3 ms
      • cpu load: < 5%
      • ram: > 90% available
      • HA interface load: < 200 kbps
      • ssd io: 1000 kw/s

      When I disable HA in kea settings, the perfdhcp test results are changing as following:

      • 500 discover packets sent
      • 499 offers received by client
        (packet capture on pfsense LAN interface and on client LAN interface confirms this figures)
      • min delay: 2 ms
      • avg delay: 9 ms
      • max delay: 42 ms

      Phase Request-Ack:

      • 499 request packets sent
      • 499 ACK packets reveived
      • min delay: 6 ms
      • avg delay: 25 ms
      • max delay: 73 ms

      Does anybody know how I can track that down to identify the reason?
      Does anybody have recommendations regarding HA with kea-dhcp that are not already in the HA documentation of the official pfsense docs?

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