11 Messages

Monday, July 21st, 2025

I am losing access ro the Internet when my PC sleeps awhile but only on Ethernet connected to Xfinity router

Windows 11 with a Realtek NIC, ethernet connected to Xfinity router (no other router n between0>  When my PC sleeps a long tim,e (hours), I lose access to the Internet through my web browsers.  All DNS lookups hang.  NSLOOKUP command does not work.  The only fix is to reboot the PC.  I tried eery PC solution I can think.  Updating windows to latest release, updating NIC driver to latest version.  Nothing helps.  I seen this problem a year ago and it went away for almost a year.  Could the Xfinity router be blocking DNS queries for some reason?

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11 Messages

1 month ago

On a laptop connected with WiFi to the same router this problem does not occur.  Also, I connected the desktop with WiFi only and it worked fine for a 24 hour period including long period of PC sleep.

Official Employee

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3.4K Messages

Hey there, @roberts452, thanks for reaching out through Xfinity Forums. I would be happy to help you with troubleshooting your connection issues. When did you start having this issue?

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11 Messages

1 month ago

It started a few wees ago.  Actually, the history is complicated.  Around three years ago when I first bought this HP OMEN desktop, there was no problem.  About 6 months later it started happening.  Then it went away for over a year.  Now the problem is back again.  I tried everything I can think of from my end:

1) Reset the network adapter

2) Updating the realtek network driver

3) Downgrading the realtek network driver to an original windows 11 level

4) Preventing the network adapter from sleeping in power management

5) Turing off power saver mode and green ethernet

6) Setting group policy to allo9 the network to be used while sleeping

7) Disable/enable the network adapter when DNS stops working.

8) Pop the ethernet cable out/in when DNS stops working.

9) I even tried killing the DNSCACHE service and recycled it.

10) Recycle the Comcast modem.

The only solution is to reboot windows 11 once the DNS gets "stuck".  The wireshark traces are consistent.  Once the DNS is stuck (timing out), there are no more UDP queries.  All DNS activity is either multicast (looks to be like apple bonjour uses MDNS) or there are attempts to communicate on port 53 using TCP.  But those exchanges do not seem to transfer data. They get closed out by the DNS server with a TCP FIN right away.

There are only two ways I can keep my DNS alive:

1) Do not allow the PC to sleep with power options (I hate that solution).

2) When I know I won't be using the PC, I disable the ethernet adapter and the WiFI takes over.  That scenario does not seem to lead to a hung DNS.  Also a laptop on a similar level of windows 11 which runs on WiFi never has a DNS hang.

This is a puzzling problem.  I am willing to gather whatever wireshark traces would be useful or other debugging.  As far as I can see, the modem and network adapter are working fine.  For example when the DNS hangs, I can still stream apple muci from an open apple music player as long as the network connection did not time out.  I can upgrade NVIDIA software drivers.  In other words, the network is transferring traffic normaly.  Just the DNS is broken.

11 Messages

1 month ago

By the way, the COMCAST modem is an XB8.

11 Messages

1 month ago

Also, when this happens both the IPV6 and IPV4 DNS servers ping just fine.  They just do not respond to either nslookup or resolve-dnsname applet.

Official Employee

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1.8K Messages

roberts452 Are you havining similar issues with other devices as well or no? 
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11 Messages

@XfinityShawn​ no!  My laptop and phone work.  But obviously they are WiFi connected.  Only the desktop is on an Ethernet connection.

11 Messages

1 month ago

By the way, Ipconfig /all shows the dns config just fine.  I also tried Ipconfig /registerdns when the problem happens and that does not help.  

Official Employee

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2.4K Messages

@roberts452

Thanks for clarifying, that sounds like a setting within your PC, have you reached out to the manufacturer of your PC to address your issues of your PC going into sleep mode and disconnecting from the Internet

I am an Official Xfinity Employee.
Official Employees are from multiple teams within Xfinity: CARE, Product, Leadership.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Please, mark a reply as the Accepted Answer.tick

11 Messages

Not a setting but it could have have the Norton firewall.  I uninstalled it and reinstalled it.  Since them the network has worked much better.

Official Employee

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1.4K Messages

I appreciate you providing an update and that everything seems to be working better now. Please let us know if anything else comes up in the future.

I am an Official Xfinity Employee.
Official Employees are from multiple teams within Xfinity: CARE, Product, Leadership.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Please, mark a reply as the Accepted Answer.tick
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