hi together,
today caused by a nic swap, i installed my opnsense from scratch.
So far so good. but i'm not able struggeling to get kea working.
Before ISC DHCP was running with the same settup without problems.
Edit: Opnsense Version 26.1.2_5
My hardware:
Lenovo M920Q, Intel X520, 1x SFP 1Gbit for WAN 1x SFP+ DAC 10gbit for LAN, 1 intel NIX for WAN2
LAN untagged, VLAN1 (smarthome, tag 20), VLAN2 homeoffice (Tag30), VLAN3 (tag40)
siwtches and ap are from unifi and support vlan and the tags are also setted up
Here is what kea shows in the log:
2026-03-01T17:10:05Warningkea-dhcp4WARN [kea-dhcp4.dhcpsrv.0x3021e665c008] DHCPSRV_NO_SOCKETS_OPEN no interface configured to listen to DHCP traffic
2026-03-01T17:10:05Warningkea-dhcp4WARN [kea-dhcp4.dhcpsrv.0x3021e665c008] DHCPSRV_OPEN_SOCKET_FAIL failed to open socket: Failed to open socket on interface vlan03, reason: failed to bind fallback socket to address 172.22.0.1, port 67, reason: Address already in use - is another DHCP server running?
2026-03-01T17:10:05Warningkea-dhcp4WARN [kea-dhcp4.dhcpsrv.0x3021e665c008] DHCPSRV_OPEN_SOCKET_FAIL failed to open socket: Failed to open socket on interface vlan02, reason: failed to bind fallback socket to address 172.21.0.1, port 67, reason: Address already in use - is another DHCP server running?
2026-03-01T17:10:05Warningkea-dhcp4WARN [kea-dhcp4.dhcpsrv.0x3021e665c008] DHCPSRV_OPEN_SOCKET_FAIL failed to open socket: Failed to open socket on interface vlan01, reason: failed to bind fallback socket to address 172.17.0.1, port 67, reason: Address already in use - is another DHCP server running?
2026-03-01T17:10:05Warningkea-dhcp4WARN [kea-dhcp4.dhcpsrv.0x3021e665c008] DHCPSRV_OPEN_SOCKET_FAIL failed to open socket: Failed to open socket on interface ix0, reason: failed to bind fallback socket to address 172.16.0.1, port 67, reason: Address already in use - is another DHCP server running?
2026-03-01T17:10:05Warningkea-dhcp4WARN [kea-dhcp4.dhcp4.0x3021e665c008] DHCP4_RESERVATIONS_LOOKUP_FIRST_ENABLED Multi-threading is enabled and host reservations lookup is always performed first.
2026-03-01T17:10:05Warningkea-dhcp4WARN [kea-dhcp4.dhcpsrv.0x3021e665c008] DHCPSRV_MT_DISABLED_QUEUE_CONTROL disabling dhcp queue control when multi-threading is enabled.
2026-03-01T17:10:05Warningkea-ctrl-agentWARN [kea-ctrl-agent.ctrl-agent.0x507f24271008] CTRL_AGENT_IS_DEPRECATED Kea Control Agent is deprecated. Its function has been moved to Kea servers.
I have found something that i need to add to LAN Network also VLAN tag.
The strange thing is that on the LAN network, the clients get an ip by dchp.
But not the range i put in at kea.
Isc dhcp isnt installed
Does anyone got an idea what i'm doing wrong?
Cheers Robert
If you installed a new fresh OPNsense 26.1.2 then your default DHCP Server is DNSmasqd.
Did you DISABLE it on ALL INTERFACES before you started using KEA DHCP Server ?
Since you have UniFi Switches and Accesspoints :
- Do you still have a UniFi Router running somewhere ?
- Did you have any DHCP Snooping rules/settings ?
- Are any of the Switches Layer 3 and thus capable of running a DHCP Server ?
- Do you have any Gen1 24-port or 48-port Switches which sometimes by mistake think they should play DHCP Server even with the latest firmware ?
(Just recently heard about this from someone so I don't have multiple confirmed sources for this one, but just mentioning it anyway!)
Thanks for your answer.
I dont run a Unifi Gateway in my Network.
I also have two old Unifi switches Running. But those arent running a dhcp.
I think out idea with dnsmasq was the right one.
It look Like dnsmasq is running and this blocks Kea from Running
My understanding was that isc dhcp is replaced my kea
And so kea is getting the standard out of the box dhcp server for opnsense.
Thanks a lot.
Cheers Robert
DNSmasq is the standard for all new deployments of OPNsense as documented:
https://docs.opnsense.org/releases/CE_26.1.html
Quotesystem: factory reset and console tools now default to using Dnsmasq for DHCP