[Kea-users] DHCPv6 flooding by Windows 11 24H2 clients

[rme at bluemail.ch]

Hi,

I am facing a quite strange issue with Windows 11 24H2 clients and Kea 
DHCPv6.

Windows seems to constantly request a new lease. This is flooding the 
logs and also putting load on DNS when I keep dynamic DNS enabled. There 
are multiple DHCP6_LEASE_RENEW per second logged.

I did neither observe this from Linux clients nor from Windows clients 
other than Windows 11 24H2.

Unfortunately I was unsuccessful tracking down this issue to a 
configuration problem. Windows 11 clients were re-installed multiple 
times. I also checked my kea configuration and looked for eventually 
missing parameters which could make Windows DHCP client fail and retry 
but was unsuccessful doing so.

Also I tried disabling DDNS but this only reducing the log spam and load 
on DNS slightly, but does not change anything about the request flood.

I also tried different renew-timer/rebind-timer and lifetime parameters. 
None of them prevent Windows to re-send multiple RENEW requests per second.

Here is my kea config:

{
"Dhcp6": {
     "interfaces-config": {
         "interfaces": [ "lan", "brkvm" ]
     },

     "multi-threading": {
         "enable-multi-threading": true
     },

     "dhcp-ddns": {
         "enable-updates": true,
         "server-ip": "127.0.0.1",
         "server-port": 53001,
         "sender-ip": "",
         "sender-port": 0,
         "max-queue-size": 1024,
         "ncr-protocol": "UDP",
         "ncr-format": "JSON"
     },
     "ddns-send-updates": true,
     "ddns-override-client-update": false,
     "ddns-override-no-update": true,
     "ddns-replace-client-name": "when-not-present",
     "ddns-generated-prefix": "client",
     "ddns-qualifying-suffix": "roelli.intranet",
     "ddns-update-on-renew": true,
     "ddns-use-conflict-resolution": false,

     "control-socket": {
         "socket-type": "unix",
         "socket-name": "/run/kea/kea6-ctrl-socket"
     },

     "lease-database": {
         "type": "memfile"
     },

     "preferred-lifetime": 604800,
     "valid-lifetime": 2592000,

     "option-data": [
         {
             "name": "dns-servers",
             "data": "fddb:9f42:7afb:1::1, fddb:9f42:7afb:1::2"
         },
         {
             "name": "client-fqdn",
             "data": "0, domain.intranet"
         },

         {
             "name": "domain-search",
             "data": "domain.local, domain.intranet"
         }
     ],

     "subnet6": [
         {
             "subnet": "fddb:9f42:7afb:1::/64",
             "interface": "lan",
             "rapid-commit": true,
             "pools": [ { "pool": "fddb:9f42:7afb:1::10 - 
fddb:9f42:7afb:1::ff" } ]
         }
     ],

     "loggers": [
     {
         "name": "kea-dhcp6",
         "output_options": [
             {
                 "output": "syslog:kea-dhcp6"
             }
         ],
         "debuglevel": 0
     }
   ]
}
}




Log examples:
Jan 24 18:23:05 master kea-dhcp6[14789]: INFO 
[kea-dhcp6.leases.139652654696128] DHCP6_LEASE_RENEW 
duid=[00:01:00:01:2e:a1:6e:10:d0:ad:08:30:3f:97], tid=0x4e84ac: lease 
for address fddb:9f42:7afb:1::27 and iaid=181447944 has been allocated
Jan 24 18:23:05 master kea-dhcp6[14789]: INFO 
[kea-dhcp6.leases.139652612753088] DHCP6_LEASE_RENEW 
duid=[00:01:00:01:2e:a1:6e:10:d0:ad:08:30:3f:97], tid=0xf02aae: lease 
for address fddb:9f42:7afb:1::27 and iaid=181447944 has been allocated
Jan 24 18:23:06 master kea-dhcp6[14789]: INFO 
[kea-dhcp6.leases.139652507895488] DHCP6_LEASE_RENEW 
duid=[00:01:00:01:2e:a1:6e:10:d0:ad:08:30:3f:97], tid=0x125d1b: lease 
for address fddb:9f42:7afb:1::27 and iaid=181447944 has been allocated
Jan 24 18:23:06 master kea-dhcp6[14789]: INFO 
[kea-dhcp6.leases.139652591781568] DHCP6_LEASE_RENEW 
duid=[00:01:00:01:2e:a1:6e:10:d0:ad:08:30:3f:97], tid=0xb792e3: lease 
for address fddb:9f42:7afb:1::27 and iaid=181447944 has been allocated
Jan 24 18:23:07 master kea-dhcp6[14789]: INFO 
[kea-dhcp6.leases.139652518381248] DHCP6_LEASE_RENEW 
duid=[00:01:00:01:2e:a1:6e:10:d0:ad:08:30:3f:97], tid=0x6b4126: lease 
for address fddb:9f42:7afb:1::27 and iaid=181447944 has been allocated
Jan 24 18:23:07 master kea-dhcp6[14789]: INFO 
[kea-dhcp6.leases.139652539352768] DHCP6_LEASE_RENEW 
duid=[00:01:00:01:2e:a1:6e:10:d0:ad:08:30:3f:97], tid=0x81b226: lease 
for address fddb:9f42:7afb:1::27 and iaid=181447944 has been allocated
Jan 24 18:23:08 master kea-dhcp6[14789]: INFO 
[kea-dhcp6.leases.139652570810048] DHCP6_LEASE_RENEW 
duid=[00:01:00:01:2e:a1:6e:10:d0:ad:08:30:3f:97], tid=0x1eb04c: lease 
for address fddb:9f42:7afb:1::27 and iaid=181447944 has been allocated
Jan 24 18:23:08 master kea-dhcp6[14789]: INFO 
[kea-dhcp6.leases.139652633724608] DHCP6_LEASE_RENEW 
duid=[00:01:00:01:2e:a1:6e:10:d0:ad:08:30:3f:97], tid=0xa550db: lease 
for address fddb:9f42:7afb:1::27 and iaid=181447944 has been allocated
Jan 24 18:23:09 master kea-dhcp6[14789]: INFO 
[kea-dhcp6.leases.139652549838528] DHCP6_LEASE_RENEW 
duid=[00:01:00:01:2e:a1:6e:10:d0:ad:08:30:3f:97], tid=0x5801f4: lease 
for address fddb:9f42:7afb:1::27 and iaid=181447944 has been allocated
...


My current version is 2.4.1.


Any ideas? Or did anybody experience similar issues before?


best regards,
Rainer