ICMP/Ping Packet Loss in Bridge Mode Only

This is a follow-up to this closed post: ‎Intermittent packet loss. | Xfinity Community Forum

The symptom is that an external router (pfSense in my case, though obviously also Unity in the referenced post) will eventually run into problems with 100% packet loss on ICMP/Ping requests. This problem occurs ONLY in bridge mode. If return to router mode (in the process getting double NAT'ed, adding power draw, slowing performance, etc.), then this problem disappears entirely.

This sounds minor, but dropped pings can cause numerous significant issues. And in my case where I'm using pfSense to provide redundant Internet connections, it completely breaks it. The Xfinity gateway is almost immediately taken offline because of this packet loss.

1) Is Comcast aware of this obviously pervasive and persistent issue? Is there any explanation as to why it would only occur if the pings aren't NAT'd behind the XFi router?

2) Has anyone tried this with a 3rd party modem (e.g., Motorola)? This would also effectively be "bridge mode"...does the problem still occur in that scenario?

Thanks

Responses

U

user_e4e953

Visitor

•

1 Message

3 years ago

I set pfsense to ping www.xfinity.com 104.65.18.248, the issues only appears on IPv4 and not IPv6, no more packet loss. System->Routing->Gateways, edit your WAN IPv4 Gateway and set Monitor IP to 8.8.8.8 or like I did.

0

flatlander3

Problem Solver

•

1.5K Messages

3 years ago

Pfsense or opnsense works fine with a cheap netgear in bridge mode for me.

I did set a couple of system tunables for ipv6:

net.inet6.icmp6.nd6_onlink_ns_rfc4861 = 1

net.inet6.ip6.accept_rtadv = 0

IPV6 is a bit wonky on Xfinity. I also set "Do not allow PD/Address release" on the WAN interface. If the release and the renew doesn't work (frequently, the server might not respond or is busy), networking is boned for the internal clients. That seems to ride with it better until it can renew. Take a look at your interfaces when it happens. They might be dropping to IPV4 only when the problem happens.

0

azdeltawye

Contributor

•

68 Messages

3 years ago

Ditch the rented Comcast/Xfinity modem/router and get a proper modem for starters...

I've been using a Motorola MB8600 in 'bridge mode' for years with pfSense without any issues. Well, except for now, see my thread below:

https://forums.xfinity.com/conversations/your-home-network/cannot-ping-comcast-gateway-ip-after-maintenance-outage/6324da992ff2c66589ffe60f

So, with the exception of my default gateway, I have no problem with ICMP on any external site.

0

U

user_5d3h48

Visitor

•

3 Messages

3 years ago

I'm really curious what Comcast does on their end that would cause this to occur but only with their modem and only in bridge mode. Seems really arbitrary, like a DoS monitoring tool that is misconfigured somehow. Will eventually likely get an MB8611 (for the 2.5gbps port), but I'm hoping to delay that for a little.

Anyway, I don't actually have IPv6 set up. I.e., I have no default gateway selected for IPv6 traffic and the IPv6 configuration type for all interfaces is set to none. Is there a specific need to enable IPv6?

2

0

flatlander3

Problem Solver

•

1.5K Messages

@ptyork No, there really isn't a need out there in the general weberverse for IPV6 only enabled sites. Someday, there might be. As of today, not really.

3 years ago

0

XfinityRay

Official Employee

•

2.8K Messages

Hello, @user_5d3h48. Thank you and the thread for this thoughtful conversation. I apologize that this issue has been persistent and understand how it would cause a problem when using the service. I would like to look at your account and run diagnostics from my end to see if that reveals the cause of this. I am not seeing this as a known issue that is being worked on so we certainly want to investigate further. Please send us a direct chat message with your full name and complete service address to “Xfinity Support”. To do so, click on the chat icon located at the top right of this forums page.

Here's the detailed steps to direct message us:
• Click "Sign In" if necessary
• Click the "Direct Message” icon (upper right corner of this page)
• Click the "New message" (pencil and paper) icon
• Type "Xfinity Support" in the to line and select "Xfinity Support" from the drop-down list
• Type your message in the text area near the bottom of the window
• Press Enter to send your message

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

3 years ago

0

U

user_e2c89e

Visitor

•

1 Message

3 years ago

I have the exact same problem. In the past few months, I've been trying to figure out why I get intermittent packet loss. Usually it's during mid day on weekends. Comcast has checked the connection and couldn't figure it out. The current theory is network traffic in the area.

My modem is a netgear CM1200. My router/network is powered by a Unifi Dream Machine Pro.

This past weekend they gave me one of their modems just to try to eliminate the chance that my modem was faulty. Their modem was set into router mode and seems to be working well for the past 48 hours. I switched it to bridge mode just now and immediately had 5-20% packet loss even after rebooting. I'm going to experiment a bit more over the next week.

9

0

SpringJMC

New Poster

•

6 Messages

@user_e2c89e , I have this problem and it is being cause by a decades old multitap in the pedestal in the yard. It has an analog pot on it. When it gets hot outside or when the sun is beating down on the pedestal, I get packet loss. I am so frustrated because I have now had 5 no show appointments to resolve this. I have had to build a sun shade for the pedestal and at times direct a fan on to the components inside of it.

Comcast is the worst company in north america for many reasons.

(edited)

3 years ago

0

U

user_5d3h48

Visitor

•

3 Messages

@user_e2c89e I haven't had the chance to test it yet (been just letting it run in router mode), but look at this bug report: Bug #5830: dpinger pings dropped by some things because of no data payload - pfSense - pfSense bugtracker

Obviously that's pfSense and not Unity, but perhaps Unity uses a similar 0bit payload on the ICMP traffic. I found that report by searching pfSense forums to find Comcast/Xfinity customers with the same problem. I believe at least one said it fixed the problem, but I don't think anyone ever said what size the ICMP payload needed to be set to.

3 years ago

0

U

user_c2f6f0

Visitor

•

1 Message

Having this same problem using a Unifi Dream machine Pro & Comcast modem/router in bridged mode.

This is clearly a Comcast bug.

3 years ago

XfinityPeterH

Official Employee

•

1.8K Messages

Hello @user_e2c89e thank you for your feedback and sad to read about your appointment no shows. Please submit a new post so we can properly help you. We appreciate you following our community guidelines.

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

3 years ago

0

CCShan

Official Employee

•

443 Messages

@user_c2f6f0 I'm sorry to hear you're experiencing issues, we'd like to look at the account equipment and signals specifically and then we can circle back here with steps taken and solutions found.

To send a "Direct Message" to Xfinity Support:
Click "Sign In" if necessary
Click the "Direct Messaging" icon or https://comca.st/3EqVMu7
Click the "New message" (pencil and paper) icon
The "To:" line prompts you to "Type the name of a person". Instead, type "Xfinity Support" there
- As you are typing a drop-down list appears. Select "Xfinity Support" from that list
- An "Xfinity Support" graphic replaces the "To:" line
Type your message in the text area near the bottom of the window
Press Enter to send it
See https://comca.st/3KQF8q9 for an example.

I no longer work for Comcast.

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

3 years ago

0

Your Home Network

user_5d3h48

ICMP/Ping Packet Loss in Bridge Mode Only

user_e4e953

flatlander3

azdeltawye

user_5d3h48

flatlander3

XfinityRay

user_e2c89e

SpringJMC

user_5d3h48

user_c2f6f0

XfinityPeterH

CCShan

New to the Community?