ISP's DHCP did not function properly - Xfinity

[jackc88]

If you constantly see the DHCP failures in the logs and router resets, a possible workaround could be to relaunch udhcpc w/o -s /tmp/udhcpc. To try a different client and obtain different logging, I swapped out udhcpc for ISC's dhclient. Packet captures and logs from both clients indicate the ISP does not honor any release or new of the DHCP leases. I don't know if this is intentional but causes havoc. Miraculously, the connection has been up for almost five days rather than going down every few hours. I don't have a proper solution yes, but the workaround is keeping the house online for work and kids' schooling w/o all the lovely spontaneous adjectives for the ISP, aka Tourette Syndrome.

For troubleshooting w/ udhcpc, I enabled syslog and send signals USR1 (to renew) and USR2 (to release). For dhclient, I run a second instance with -r in attempts to perform a release. Let me know if anyone needs the test script I use to modify DHCP. By the way, I am running "dual-stack" with the ISP, and I never saw the issue on the IPv6 side w/ odhcp6c.

If anyone sees any incorrect assumptions on my part, please do share. Xfinity just switched to a new web portal, but if you want more details, please see the following link, Xfinity Internet - LoS ( Provisioning and DHCP ) | Xfinity Community Forum.

Model	RT-AX58U
Firmware Version	386.1_2
Firmware Build	Fri Feb 12 22:47:24 UTC 2021 merlin@5da5b4c
Bootloader (CFE)	0.0.0.5
Driver version	wl0: Jan 16 2021 03:23:07 version 17.10.121.37 (r789389) b567bc9

 

[MrRederick]

I see this about once a week on my UK Virgin Media connection. Is your XFinity also a DOCSIS cable service? I have had some relief using the "DHCP query frequency" set to Continuous mode in the WAN settings. I have an RT-AX88U with RMerlin's 386.1_2. I can't correlate the problems with any logs in my cable modem (VM Hub 3.0) but my guess is that the ASUS built in udhcpc is not tolerant of transient issues on the cable segment.

 

[jackc88]

@MrRederick : Thanks for the input. Xfinity does also use DOCSIS. Apparently, changing the frequency on my end exacerbated the issue. At first, I tried different parameters and finally realized the issue was "the script" that was being called that would knock out connectivity. Even though I have switched to dhclient, I believe preventing script from being called solves the issue in the interim with the ISP's DHCP issues. I do however can see how increasing the frequency can help under certain conditions. Thanks again