Visitor
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3 Messages
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
user_e4e953
Visitor
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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.
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flatlander3
Problem Solver
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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.
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azdeltawye
Contributor
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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.
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user_5d3h48
Visitor
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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?
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user_e2c89e
Visitor
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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.
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