Hi,
How is it that the vms acquire ip using secondary server? does the
secondary bind on the same interface at the same time?
Logs should be under /kea/install/path/var/log/kea
I think that only one of your servers successfully binds to the
interface and because the server uses reuse port/address the secondary
if starts second will receive traffic.
------------------------------------------------------------------------
*From: *Stuart <[email protected]>
*To: *kea-users <[email protected]>
*Date: *Saturday, 21 February 2026 3:31 AM EET
*Subject: *[Kea-users] Kea DHCP4 not working on newly configured
bridged network
Good Morning,
I am running Ubuntu 24.04, Kea 2.4.1. I have been using Kea
without major issues for a year or two, isc-dhcp for a couple of
years prior. During recent kernel updates I decided I was sick of
Virtualbox compatibility issues, so I created a bridged network so
that I could move my vms (Nextcloud, Stork) to KVM. I am somewhat
incompetent, but after about 100 attempts I have managed to setup
a bridged network that connects my server to the rest of the
network and to the internet. My new KVM VMs are joining the
network as if they were real devices. My problem is my kea DHCP4
server. I guess have done something stupid, either with selecting
the interface in kea-dhcp4.conf or with configuring my bridged
network (br0). At this stage, when I start kea-dhcp4-server, it
communicates to my HA standby to to take control of DHCP but then
completely fails to provide ip addresses itself. So, the network
currently looks like this:
/dad@macserver:~$ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state
UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host noprefixroute
valid_lft forever preferred_lft forever
2: enp34s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc
fq_codel master br0 state UP group default qlen 1000
link/ether 2c:f0:5d:2d:88:35 brd ff:ff:ff:ff:ff:ff
3: br0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue
state UP group default qlen 1000
link/ether 42:4c:23:6c:4d:7f brd ff:ff:ff:ff:ff:ff
inet 192.168.1.104/23 brd 192.168.1.255 scope global
noprefixroute br0
valid_lft forever preferred_lft forever
inet6 fe80::e54c:73f4:f662:95fb/64 scope link noprefixroute
valid_lft forever preferred_lft forever
4: virbr0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc
noqueue state DOWN group default qlen 1000
link/ether 52:54:00:5b:e6:4e brd ff:ff:ff:ff:ff:ff
inet 192.168.100.1/24 brd 192.168.100.255 scope global virbr0
valid_lft forever preferred_lft forever
5: vnet0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue
master br0 state UNKNOWN group default qlen 1000
link/ether fe:00:27:dc:06:7e brd ff:ff:ff:ff:ff:ff
inet6 fe80::fc00:27ff:fedc:67e/64 scope link
valid_lft forever preferred_lft forever
6: vnet1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue
master br0 state UNKNOWN group default qlen 1000
link/ether fe:54:00:80:eb:73 brd ff:ff:ff:ff:ff:ff
inet6 fe80::fc54:ff:fe80:eb73/64 scope link
valid_lft forever preferred_lft forever/
The key sections (eliminating all my lease reservations and such)
of my dhcp4.conf look like this:
/{
"Dhcp4": {
"interfaces-config": {
"interfaces": [ "br0" ]
},
"control-socket": {
"socket-type": "unix",
"socket-name": "/run/kea/kea4-ctrl-socket"
},
"lease-database": {
"type": "memfile",
"lfc-interval": 3600
},
"multi-threading": {
"enable-multi-threading": true,
"thread-pool-size": 2,
"packet-queue-size": 14
},
"client-classes": [
{
"name": "homeauto"
},
{
"name": "normal",
"test": "not member('homeauto')"
}
],
"option-data": [
{
"space": "dhcp4",
"name": "domain-name",
"code": 15,
"data": "skfaf.servesarcasm.com"
},
{
"space": "dhcp4",
"name": "domain-name-servers",
"code": 6,
"data": "192.168.1.1"
},
{
"space": "dhcp4",
"name": "broadcast-address",
"code": 28,
"data": "192.168.1.255"
},
{
"space": "dhcp4",
"name": "routers",
"code": 3,
"data": "192.168.1.1"
},
{
"space": "dhcp4",
"name": "subnet-mask",
"code": 1,
"data": "255.255.254.0"
}
],
"valid-lifetime": 43200,
"renew-timer": 21600,
"rebind-timer": 32400,
"expired-leases-processing": {
"reclaim-timer-wait-time": 3600,
"hold-reclaimed-time": 172800,
"max-reclaim-leases": 0,
"max-reclaim-time": 0
},
"dhcp-ddns": {
"enable-updates": false
},
"authoritative": true,
"hooks-libraries": [
{
"library":
"/usr/lib/x86_64-linux-gnu/kea/hooks/libdhcp_lease_cmds.so"
},
{
"library":
"/usr/lib/x86_64-linux-gnu/kea/hooks/libdhcp_stat_cmds.so"
},
{
"library": "/usr/lib/x86_64-linux-gnu/kea/hooks/libdhcp_ha.so",
"parameters": {
"high-availability": [ {
"this-server-name": "macserver",
"mode": "hot-standby",
"heatbeat-delay": 10000,
"max-response-delay": 60000,
"max-ack-delay": 5000,
"max-unacked-clients": 5,
"sync-timeout": 60000,
"multi-threading": {
"enable-multi-threading": true,
"http-dedicated-listener": true,
"http-listener-threads": 0,
"http-client-threads": 0
},
"peers": [
{
"name": "macserver",
"url": "http://192.168.1.104:8003/";
<http://192.168.1.104:8003/>,
"role": "primary"
},
{
"name": "oldhp",
"url": "http://192.168.1.110:8003/";
<http://192.168.1.110:8003/>,
"role": "standby"
}
]
} ]
}
}/
//
/],
"shared-networks": [
{
"name": "macnet",
"subnet4": [
{
"id": 1,
"subnet": "192.168.1.0/24",
"pools": [
{
"pool": "192.168.1.124 - 192.168.1.198",
"client-class": "normal"
}
],
"option-data": [
{
"space": "dhcp4",
"name": "routers",
"code": 3,
"data": "192.168.1.1"
}
]
},
{
"id": 2,
"subnet": "192.168.0.0/23",
"pools": [
{
"pool": "192.168.0.150 - 192.168.0.175",
"client-class": "homeauto"
}
],
"option-data": [
{
"space": "dhcp4",
"name": "routers",
"code": 3,
"data": "192.168.1.1"
},
{
"space": "dhcp4",
"name": "domain-name-servers",
"code": 6,
"data": "192.168.1.1"
}
]
}
]
}
],
"loggers": [
{
"name": "kea-dhcp4",
"output_options": [
{
"output": "/var/log/kea-dhcp4.log",
"maxsize": 2048000,
"maxver": 4
}
],
"severity": "INFO",
"debuglevel": 0
}
]
}
}/
I changed my "interface" to "br0" because my previous setup (exerp
below) stopped working when I started the br0 network.
/{
"Dhcp4": {
"interfaces-config": {
"interfaces": [ "enp34s0" ]/
Changing the interface to "br0" has had exactly no effect.
I realise that I have missed something fundamental and I am
wasting your valuable time. However I have been trying to sort
this out for days (in whatever spare time is available) and I have
acheived nothing. Each time I start kea-dhcp-server on my main
server it appears in Stork with no errors, systemd says its
running fine and my HA standby stops providing dhcp. Unfortunately
if I then turn on a device it simply does not receive an ip lease.
If I turn off DHCP on the main server then eventually the standby
starts takes over dhcp again and network functions return to
normal (though this takes a very long time & sometimes requires a
restart of kea-dhcp4-server on the stanby server, perhaps another
error to fix later). Even my new VMs receive ips seamlessly from
the standby server.
If you need to see some logs, please tell me where I can retreive
them because I haven't been able to work that out either (I think
I need to change my logging parameters in kea-dhcp4.conf). I used
Wireshark to capture network coms before and after turning on the
main dhcp server but I then realised that I was too
stupid/ignorant to work out what was going on from the output. I
can provided the Wireshark output, but it is a large file (ran it
for too long and filtered it poorly, I think) that I won't inflict
on you unless you wish it.
Please give me some ideas of what I have to do to troubleshoot/fix
this.
Regards
Stuart MacGregor
