At the end of every month my WAN DHCP lease gets reduced to 2 hours

@flatlander3​ Thank you for additional insight.  I hadn't seen disabling IPv6 as a solution/mitigation before; unfortunately turning off IPv6 does not solve or mitigate my issue.  Techs have looked at my line, too, and they say all is good, so the problem does not exist there.  My equipment is all still up to date too.  And yeah, it does end up being a nuisance in the end, but it still makes P2P for work and other things like online games built off .6s turn around times annoying to interact with if the connection drops every 90 minutes.  It looks like I will need to continue arguing with Xfinity support to find out why now it is normal that they are destroying the DHCP times during the final week of each month.  I will also need to watch and see if this problem still persists during the "good lease" periods, it should be normal again in like a week based on the past couple months

@user_deae5f​  Line conditions are going to change over time.  They also change when they change something in your neighborhood.  A drunken neighbor smoked the cable box with a car in the neighborhood, and my signal power doubled overnight.  This was causing spontaneous reboots and errors.

I ended up fixing my own issues after being told it was fine.  To tame the signal power down, I installed an attenuator, but also there was a lightning suppressor installed that had seen better days, and too many voltage spikes.  That was interfering with upstream power too.  Cheap comscope splitters Xfinity uses are a bit iffy too and degrade over time.

Might look fine on their little cable tester, but what matters is what your modem/gateway sees.  Go through the link above.  If you log into your gateway or modem, take a look at the signal tables and error logs.  There might be something going on there.  If you post error logs, redact the MAC addresses or the forum bot will mark it private and nobody will see it.  The signal table might help too.

@user_deae5f​ I suggest disabling IPV6 because there was a massive problem with that for months here.  I don't know what the problem was on their end, but frequently, their server just didn't respond.  I've see that at another location with another comcast banner company too.

On a rebind, if you drop a lease before the rebind, then try a renew but get nothing, everything on your LAN looking for an IPV6 gateway will be boned on routing until the lease comes back.  More than enough time would pass so all active state connections would die.  If you can debug that conversation with your equipment, you can actually see that happen.  You wouldn't be able to with a modem or gateway, but I can catch it in the debug logs on my stuff and watch my fail-over ISP take over in that case.

@flatlander3​ 
I went through that post for everything that I could look at.  My line appears fine.  I don't have any splitters on it, it's just a straight coax from the wall to the modem.  Unfortunately, I'm on one of their xFi gateways for the time being and while I can see that the signal levels are within expected ranges, it doesn't seem to be keeping any logs.  Maybe it's because of the fact I have it in bridge mode or maybe it flushes everything because I can't get into it without rebooting said gateway.  I'm unfortunately stuck with this for the time being.  One part old modem not fitting spec anymore from a recent service upgrade, another part accepting it so that maybe comcast is willing to help more.  My new one was supposed to arrive today, but now that's on backorder for a month.  However this issue did persist before I upgraded my service and while I was on the old modem the past two months (September and October) that I also had this issue during only the final week of the month.  From what I remember from there, I had next to no timeouts, not even ones that coincided with DHCP renewals. 

I think I can see what you are talking about with the rebind issue and IPv6.  If I watch my router status while either I trigger a renewal or during a renewal from a lease expiring, it will drop it completely and take at least 10 seconds to get a new lease from my timings.  However, there is no difference between IPv6 being enabled or not.  I will leave disabled for the time being.

This seems very much like the solution to the problem is out of my hands, given that it appears to be equipment agnostic and this shortened DHCP lease just seems to be scheduled for the end of the month or every 4th week now

@user_deae5f​  Just for information, the management interface in bridge mode on most of them ends up at http://192.168.100.1  

Xfinity gear may have crippled logs, or no log these days, but the signal table should be there.  

@XfinityDemitrius​ 

I have worked previously with support over the phone while attempting to troubleshoot this back during the week of Otober 30th and at the end of September, as well.  In October, I was using my own modem, then I picked up the xFi gateway at the request of support.  Between those two devices with the xFi gateway being in both bridge mode and non-bridge mode I still ran into this renewal issue.  Eventually it just fixed itself towards the end of the week.  However I am unhappy about the pattern that I am seeing arise where it seems that starting the final week of the month, my DHCP lease gets reduced down to 2 hours from the usual 4 days.  How do I work with you to get a more permanent solution to this issue?

We are glad to take a closer look at this for you today @user_deae5f.  Please feel free to shoot us a private message so that we can get your info and get started.  

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