Visitor
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4 Messages
X7 No Connectity via Ethernet devices but WiFi functions normally
I have an X7 gateway (Arris TG4482A) serving as the router and Wi-Fi access point for approximately 30-40 devices at any given time (and around 110-120 different devices over the 7 months since it was installed). The devices connect through a roughly 50/50 mixture of Wi-Fi and Ethernet connections. The Ethernet connected devices are all run through unmanaged gigabit switches in 4 different rooms, each of which is connected to a hub switch. The hub switch is also connected directly two devices and the gateway (which has 2 devices directly connected to it). The gateway is set up with default settings — it manages DHCP (IP addresses 10.0.0.2 through 10.0.0.253) and the subnet is 255.255.255.0.
This setup functioned without any issues until last week, when suddenly (almost) all of the ethernet connections stopped being able to connect to the internet or see other devices in the network but the devices connected over WiFi all continue to function normally without any issues. Only those devices directly connected to the hub switch or directly to the gateway can function over Ethernet. And even then one device connected to the hub switch does not work. No new devices were added to the network.
Looking at the AppleTVs which are connected via Ethernet I see that the gateway is putting the device on a different subnet 255.255.0.0 and assigning an IP address of 169.264.20.2XX. These devices don’t have internet access and do not show up on the gateway as being connected — despite all showing an active Ethernet connection.
Customer service suggested my x7 cannot handle the number of devices, but I am nowhere near the client limit. I’ve tried swapping out the hub switch and well as the switches in individual rooms without any luck.
I have the same setup in another home but using Ubiquity/ UnFu hardware and the x7 in bridge mode without any issues.
My initial guess was a bad switch(es) or a rouge DHCP sever but I haven’t been able to identify either. Since this setup worked for 7 months without issue it seems like a hardware failure — but I know just enough networking to be Dani so it’s also possible/likely I’m missing something obvious.
Accepted Solution
zandor60657
Contributor
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204 Messages
3 years ago
Netgear and TP-Link both don't work? Ok, not the switch. Netgear is one of the top brands if not the top brand for unmanaged home switches and TP-Link is good too. Both of those incompatible? Incomprehensible.
Given that you're already in the UniFi ecosystem I'd just go with that as long as you're happy with it.
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Zorgonas
Regular Visitor
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12 Messages
3 years ago
Same issue. Started yesterday after more than a year working fine.
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zandor60657
Contributor
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204 Messages
3 years ago
169.254.x.y is an IPv4 autoconfiguration address. The devices are assigning those addresses to themselves since they aren't getting a response from DHCP. Windows does the same thing. Either the DHCP server in the XB7 isn't working or the network is down.
It's possible to "pause" a device in the Xfinity app, which basically kicks it off the network. You might want to check that just in case something went nuts and paused a bunch of devices.
You could try giving a computer (or other device) connected via ethernet (turn WiFi off if it has it) a static address on the 10.0.0.0/24 network just to see if it works. You'll need to set the DNS servers as well for Internet access. If that works it's probably a DHCP problem. That would suggest there's an issue with the XB7. Maybe it crashed or has a corrupt DHCP leases database. Normally routers store leases in flash memory so they can survive a power cycle. My best guess on fixing it would be try a factory reset of the XB7.
Another thing you could try is just pinging around the network. Devices with 169.254.0.0/16 addresses should be able to talk to each other if the network is working. Computers, smart phones, the XB7 and any other devices that support IPv6 will also have link-local addresses (they start with fe80:) you can try to ping. The XB7 and computers that don't have a firewall configured to block it will respond to ping. Phones tend to not respond, but you can ping from one (probably have to download a ping app).
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XfinityEmilyB
Official Employee
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2K Messages
3 years ago
Welcome to our community forum, @user_d20a03 and thank you for the helpful tips, @zandor60657! Were you able to try the factory reset to see if the issue persists?
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user_d20a03
Visitor
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4 Messages
3 years ago
The factory reset did not work. Nor did replacing the gateway. I’ve done some more testing and I’m pretty much certain comcast made software changes that broke the x7.
Xfinity support told me the issue was that an x7 gateway cannot handle the number of devices and that I would need an x8. After that conversation I went as directed to the Xfinity store only to be told the store is not allowed to give customers x8 gateways because they keep giving them to customers who don’t have gigabit service; instead the store told me they would mail me the x8. Then they mailed me an x7. The new x7 gateway has the exact same problems. So it’s still possible or likely something in the x7 is causing this problem.
After setting up the new x7 I did some more extensive testing, I’m 99% sure this is a software bug with the x7 gateway and certain devices when using a switch. The x7 connects to my main switch and it’s DHCP server issues IP address for some devices directly connected to the main hub switch (HD home run, UniFi AP) but not others (I tried 3 separate AppleTVs and a PC). I swapped the devices I was testing with into the same port on the switch to eliminate that as a potential issue and used two different switches. Then I used an inline connector to link the x7’s cat6 cable that runs to my hub switch directly to cat6 cables in each room with the the appleTVs to bypass the hub switch. Under that setup the ATV worked.
This seems to have isolated the problem to the x7 when connected to certain devices using a switch. Since the x7 plus switches work for other devices and the x7 works with a direct connection the ATVs, I can rule out faulty switches and faulty ports on the the ATV devices as well as hardware problems in the x7. Seems like the only explanation I can think of is a software issue on the x7.
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zandor60657
Contributor
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204 Messages
3 years ago
I suspect your problem is an XB7 DHCP server issue, but I can't be sure without coming by your house and playing around with a packet sniffer. The only other thing I can think of is maybe the XB7 and your switches don't get along, but that seems unlikely unless you're using something weird or high end and they're all the same or similar. If they're ordinary 1Gb unmanaged switches having an issue like this is kind of unheard of. If we're talking an enterprise managed L3 switch there are all kinds of ways in can break things in bizarre ways. That's probably not it, but I've been in the IT business for a couple decades and I've seen far stranger things.
I don't know how much you've looked around these forums but there are a lot of XB7 issues after recent changes. Lots of app problems, they retired the web site, and it's not just port forwarding or this we're not really sure what it is problem you're having with wired devices. Another really big one is people having trouble with 2.4Ghz only devices connecting to an SSID that's both 2.4 and 5GHz. Seems like another bug to me... I have plenty of old 2.4Ghz only stuff and no issues with a single SSID for both frequencies, but I'm not using Comcast equipment. I bought my own gear a while ago and I've dodged all these issues. You might want to think about it.
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user_d20a03
Visitor
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4 Messages
3 years ago
Thank you for the help and suggestions. I’m running generic, cheap gigabit switches from TPlink and Netgear and everything has worked perfectly for months without issue. I did find one bad switch (or bad port on the switch) from all of my testing but swapping it out didn’t fix any of the problems. Seems to me that this a bizarre x7 issue, most likely attributable to the recent changes and certain combinations of hardware.
I have another x7 at my primary residence with an exactly identical network structure (and the same negrear/TPlink switches) expect that the x7 runs in bridge mode with an ubiquiti edgerouter and UniFi APs and I’ve had zero issues. I’ll probably end up switching over to a UniFi Dream machine and abandon the x7 unless Xfinity figures this out.
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user_d20a03
Visitor
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4 Messages
3 years ago
Moving the x7 to bridge mode and using a UniFi UDM router fixed everything immediately. Since the problem persisted on two different x7 gateways, it seems clear that Xfinity made software changes that broke basic network functionality.
It’s infuriating that I have to spend weeks and $400 fixing a problem that Xfinity created just to get my service back to where it was in April.
I will also say that the x7 Wi-Fi range and throughput is far better than the UDM. I’ll have to add some APs and tinker with the settings to get back to the same level of coverage.
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