802-11r (Fast Roaming) Lost IP

I have 2 xiaomi AX 3600 that run the Image of robimarko. So far so good.
I have try to setup 802-11r like https://www.reddit.com/r/openwrt/comments/515oea/finally_got_80211r_roaming_working/

When a client is switch from one AP to the other one it lost his IP.
I have debug it with tcpdump.

The dhcp request and the dhcp response are seen on the dhcp-server but the response is not seen at the new AP.

The cable setup is as follows:

WAN --- Router/DHCP --- switch --- AP1
                           |------ AP2


this is not how FT works, you should not see any new DHCP request at all. purpose of FT is that client seamlessly (at least much faster) connects from ap1 to ap2, keeping ip address, network up with really minimal service disruption. basically you should not experience any network hiccups (maybe some).

But FT must be supported by your clients foremost, they initiate the roaming by default. If your client is sending DHCP request because lost its IP address, then most probably your client does not support FT roaming and/or incompatible with your AP settings (e.g WPA3 and FT may not work very well).

Also you are referring to a 6years old post, i suggest to search in this forum or wiki first if you are using openwrt for up to date content.

That post's still relevant, at least for 19.07.

I followed it long time back, when I set it up on my C2600s.

@Basti fire up some wifi analyzer app on Android, see if shows the +FT attribute for your wifi.
Check out 802.11r Fast Transition how to understand that FT works? and the pics there.

as OP did not specify much detail regarding his/her setup it is hard to judge if that post is relevant or not. on its own it is on 19.x very likely, as i also learned from it at the time. but on 21.x it is automagically works out of box without the need to set any mobility domain and co (if every client and ap supports FT but it's not owrt to blame if not).

The +FT is show in the wifi app.
OpenWRT version:

Firmware Version	OpenWrt SNAPSHOT r18429-6ccdf9a7f1 / LuCI Master git-22.046.84457-2178444
Kernel Version	5.10.83

wifi config:

root@ap1:~# cat /etc/config/wireless 

config wifi-device 'radio0'
	option type 'mac80211'
	option path 'soc/20000000.pci/pci0000:00/0000:00:00.0/0000:01:00.0'
	option channel '36'
	option band '5g'
	option htmode 'VHT80'
	option disabled '1'

config wifi-device 'radio1'
	option type 'mac80211'
	option path 'platform/soc/c000000.wifi'
	option band '5g'
	option cell_density '0'
	option htmode 'HE80'
	option channel '36'

config wifi-device 'radio2'
	option type 'mac80211'
	option path 'platform/soc/c000000.wifi+1'
	option band '2g'
	option htmode 'HE40'
	option channel '6'
	option country 'DE'
	option cell_density '0'
	option txpower '20'

config wifi-iface 'default_radio2'
	option device 'radio2'
	option network 'lan'
	option mode 'ap'
	option ssid 'myssid'
	option key 'changeme'
	option encryption 'psk2'
	option mobility_domain 'secret'
	option ft_psk_generate_local '1'
	option ieee80211r '1'
	option ieee80211k '1'
	option ieee80211v '1'
	option bss_transition '1'
	option pmk_r1_push '1'
	option disassoc_low_ack '0'
	option ft_over_ds '0'

config wifi-iface 'wifinet2'
	option ssid 'myssid_5G'
	option encryption 'sae-mixed'
	option device 'radio1'
	option mode 'ap'
	option network 'lan'
	option key 'changeme'
	option disassoc_low_ack '0'


I had to add option reassociation_deadline '20000' before 802.11r started to work reliably on my network.