XB10 dropping IPv6 FORWARD traffic — breaks IPv6 services, persists across resets

@XfinityDena​

Thanks Dena. I’ve done extensive troubleshooting already, so here’s the full picture to save us both time.

The problem: my XB10 gateway is dropping IPv6 FORWARD traffic to my LAN devices, which breaks IPv6-dependent services like YouTube while IPv4 traffic works normally.

What I’ve already tested and ruled out:

1. Confirmed it is the gateway, not my devices. The same services fail on my home network across multiple devices (PS5, phone) but work instantly on those same devices over cellular.

2. Checked the gateway’s own firewall logs (Troubleshooting, Logs, Firewall). They show FW.IPv6 FORWARD drop and FW.IPv6 INPUT drop entries climbing into the thousands during the failures. In one 45 minute window the FORWARD drops went from 480 to 2,791. I have timestamped logs and can share them.

3. The drops occur under the default Typical Security IPv6 firewall setting, and also under Custom Security with the firewall disabled. So it is not a firewall configuration I can fix on my end.

4. It survives reboots, power cycles, and full resets, and persists across firewall security levels. That rules out a transient state issue and points to firmware.

5. Changed DNS (Cloudflare and Google) and set MTU to 1450 on the affected device. No change.

This matches the documented IPv6 routing issue reported across XB series gateways. Given all of the above, what I’m asking for is one of two things: (a) escalation to network engineering for a firmware check on my XB10 and region, with a ticket number I can track, or (b) a swap to a different gateway model to confirm the XB10 firmware is the cause. A standard modem reset or refresh won’t help, since I’ve already done that repeatedly.

user_jr25y1 Hmm, we are able to take a deeper dive on the diagnostics from our end. Could you please send our team a direct message with your full name and full address? Our team can most definitely take a further look at this issue.

To send a Direct message:
Click "Sign In" if necessary
• Click the "Direct Message" icon
• Click the "Start New Conversation" (pencil and paper) icon
• Type "Xfinity Support" in the "To:" line and select "Xfinity Support" from the drop-down list which appears.

@EG​ I had to disable IPv6 from my router (XB8 is in bridge mode) and everything started working. Seemed to be a routing issue. I would run a trace route to any IPv6 host out on the internet and it would drop after a few hops.

@user_fk1wdl​ 

Are you the original poster @user_jr25y1 ??

Sorry, user_fk1wdl was me, didn't realize I got logged into a different Xfinity account that I also manage. Sorry for the confusion.