ALL TP Link Access Points ignore DCHP Lease length in "Dynamic IP" mode + constantly renew their IP
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When a TP Link Access Point is set up in Lan Settings "Dynamic IP" mode it appears to ignore the lease time given to it by the DHCP server, and constantly renews the lease every 30-60 seconds. This results in bloated system logs full of IP renewal log lines. Eventually this could cause a router to run out of memory depending on its log retention policy.
Note: I have selected Model AX72 in the form above, but this seems to affect ALL TP Link Access points that I have tested so far (AX72 + AV600 Powerline Extender)
I can see that it also affects other AX models & Deco units as evidenced by the following threads
https://community.tp-link.com/us/home/forum/topic/99514
https://community.tp-link.com/us/home/forum/topic/535486?replyId=1115100
My guess is that this is a bug/feature in the DHCP client code which I would expect is shared by all of these devices.
Steps to replicate
- Set the DHCP server lease time to a large number on your router (I used 10 hours/600 minutes on my ER605 Router)
- Set a TP Link Access Point into "Dynamic IP" mode
- Observe in Router or Access Point System logs how the Access Point believes that half the lease time has passed and renews the lease every 30-60s, regardless of what lease time is actually set
- Set the TP Link Access Point into "Static IP" mode
- Observe in the Router or Access Point System logs how the Access Point no longer renews the lease every 30-60s (Note this is expected as the lease would be granted indefinitely anyway so no renewal is necessary).
(image: Router system logs showing my AX72 192.168.1.3 and AV600 Powerline Wifi Extender 192.168.1.4 constantly renewing their IPs)
Impact: Excessive IP renewal fills up Router System Logs potentially crashing the router due to lack of memory dependent on its retention policy
Expected behavior: I would expect the "Dynamic IP" mode to respect the lease time given to it by the DHCP server, and only renew the lease when it is due to expire or is half way through it as the logs lead me to believe is meant to happen. This is how all other non TP Link devices using "Dynamic IP" on my network behave.
