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AX20 DHCP client ignores server's lease time and renews every 30 seconds

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AX20 DHCP client ignores server's lease time and renews every 30 seconds

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AX20 DHCP client ignores server's lease time and renews every 30 seconds
AX20 DHCP client ignores server's lease time and renews every 30 seconds
2022-02-23 08:28:16
Model: Archer AX20  
Hardware Version: V1
Firmware Version: 1.3.5 Build 20211231 rel.63820(5553)

I'm using my Archer AX20 in WAP mode. If I set the IP address mode to dynamic, the router ignores the offered lease time of 259200 seconds (72 hours) and instead attempts to renew its lease every 30 seconds. This fills the disk on my DHCP server as it logs each DHCP request. A tcpdump (WireShark) dump of the exchange follows. Note the timestamps.

 

23:54:37.344100 IP (tos 0x0, ttl 64, id 23651, offset 0, flags [DF], proto UDP (17), length 399)
    10.96.0.250.bootpc > orifice.lsi.lan.bootps: [udp sum ok] BOOTP/DHCP, Request from 60:32:b1:a6:be:ac (oui Unknown), length 371,
          Client-IP 10.96.0.250
          Client-Ethernet-Address 60:32:b1:a6:be:ac (oui Unknown)
          Vendor-rfc1048 Extensions
            Magic Cookie 0x63825363
            DHCP-Message Option 53, length 1: Request
            Client-ID Option 61, length 7: ether 60:32:b1:a6:be:ac
            MSZ Option 57, length 2: 1024
            Parameter-Request Option 55, length 10:
              Subnet-Mask, Default-Gateway, Domain-Name-Server, Hostname
              Domain-Name, BR, Static-Route, NTP
              Classless-Static-Route, Classless-Static-Route-Microsoft
            Vendor-Class Option 60, length 8: "MSFT 5.0"
            Hostname Option 12, length 10: "ArcherAX20"
23:54:37.344561 IP (tos 0x0, ttl 64, id 51815, offset 0, flags [DF], proto UDP (17), length 328)
    orifice.lsi.lan.bootps > 10.96.0.250.bootpc: [bad udp cksum 0x1783 -> 0x88e4!] BOOTP/DHCP, Reply, length 300, xid 0x28a89f4f, Fl
          Client-IP 10.96.0.250
          Your-IP 10.96.0.250
          Server-IP orifice.lsi.lan
          Client-Ethernet-Address 60:32:b1:a6:be:ac (oui Unknown)
          Vendor-rfc1048 Extensions
            Magic Cookie 0x63825363
            DHCP-Message Option 53, length 1: ACK
            Server-ID Option 54, length 4: orifice.lsi.lan
            Lease-Time Option 51, length 4: 259200
            Subnet-Mask Option 1, length 4: 255.255.0.0
            Default-Gateway Option 3, length 4: zyxel.lsi.lan
            Domain-Name-Server Option 6, length 8: rocinante.lsi.lan,orifice.lsi.lan
            Domain-Name Option 15, length 7: "lsi.lan"
            NTP Option 42, length 8: rocinante.lsi.lan,orifice.lsi.lan
23:55:11.457252 IP (tos 0x0, ttl 64, id 27326, offset 0, flags [DF], proto UDP (17), length 399)
    10.96.0.250.bootpc > orifice.lsi.lan.bootps: [udp sum ok] BOOTP/DHCP, Request from 60:32:b1:a6:be:ac (oui Unknown), length 371,
          Client-IP 10.96.0.250
          Client-Ethernet-Address 60:32:b1:a6:be:ac (oui Unknown)
          Vendor-rfc1048 Extensions
            Magic Cookie 0x63825363
            DHCP-Message Option 53, length 1: Request
            Client-ID Option 61, length 7: ether 60:32:b1:a6:be:ac
            MSZ Option 57, length 2: 1024
            Parameter-Request Option 55, length 10:
              Subnet-Mask, Default-Gateway, Domain-Name-Server, Hostname
              Domain-Name, BR, Static-Route, NTP
              Classless-Static-Route, Classless-Static-Route-Microsoft
            Vendor-Class Option 60, length 8: "MSFT 5.0"
            Hostname Option 12, length 10: "ArcherAX20"
23:55:11.457568 IP (tos 0x0, ttl 64, id 64110, offset 0, flags [DF], proto UDP (17), length 328)
    orifice.lsi.lan.bootps > 10.96.0.250.bootpc: [bad udp cksum 0x1783 -> 0x88e4!] BOOTP/DHCP, Reply, length 300, xid 0x28a89f4f, Fl
          Client-IP 10.96.0.250
          Your-IP 10.96.0.250
          Server-IP orifice.lsi.lan
          Client-Ethernet-Address 60:32:b1:a6:be:ac (oui Unknown)
          Vendor-rfc1048 Extensions
            Magic Cookie 0x63825363
            DHCP-Message Option 53, length 1: ACK
            Server-ID Option 54, length 4: orifice.lsi.lan
            Lease-Time Option 51, length 4: 259200
            Subnet-Mask Option 1, length 4: 255.255.0.0
            Default-Gateway Option 3, length 4: zyxel.lsi.lan
            Domain-Name-Server Option 6, length 8: rocinante.lsi.lan,orifice.lsi.lan
            Domain-Name Option 15, length 7: "lsi.lan"
            NTP Option 42, length 8: rocinante.lsi.lan,orifice.lsi.lan
 

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#1
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Re:AX20 DHCP client ignores server's lease time and renews every 30 seconds
2022-07-22 09:05:17 - last edited 2022-07-22 09:50:03

  @SpareSimian I had a good debugging session with TP Link Support around a similar issue. It's not unique to the AX20 and seems to be an issue with TP Link Access Points across the board.

 

My issue was I had an ER605 Router, with two TP Link access points (one AX72 and one powerline based wifi extender). Both were constantly renewing their IP leases every 30-60s, yet no other client seemed to. The IP leases were set to 10 hours and the Access Points were refreshing after 30-60 seconds which was filling up the system logs.

 

I tried setting static + dynamic IP reservations ER605 side but with no success. I then saw this thread + https://community.tp-link.com/us/home/forum/topic/99514 and tried setting the Access Points to "Static IP" access point side and the issue suddenly stopped.

 

Solution: Use a Static IP Access Point side.

 

I've reported it as a bug to TP Link, lets hope it gets fixed and isnt a feature :)

https://community.tp-link.com/us/home/forum/topic/573370?page=1

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#2
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Re:AX20 DHCP client ignores server's lease time and renews every 30 seconds
2022-07-22 16:55:20

  @ed0906 Thanks for confirming and filing a bug. I did switch to a static address to stop the DHCP server log from filling.

 

I'm currently using the ISC Kea DHCP server on my CentOS 7 Linux server to supply addresses on my home LAN. (CentOS 7 comes with ISC's older DHCP server that most distros use, but they now focus their development on their new Kea code base, so I installed that for better support. You can install it alongside the old one and migrate your configuration over (the new one is JSON-based) using a utility, then stop the old service and start the new one. There's no lease migration ability but my LAN is small and my systems were all on to check for an address in use at their next renewal so I didn't have any address conflicts when I switched over.) 

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#3
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