Question about Xfinity Gig Service Speedtest Throttling
Question about Xfinity Gig Service Speedtest Throttling
Hello everyone. I’m reaching out to the PC demigods for help.
My old gaming PC, a couple years back, had download speeds over 700 Mbps. It was hardwired to a switch, which in turn was connected to the Xfinity Gateway. Recent speed tests showed consistently above 800 Mbps.
Two days ago, nothing changed—just 92 MBPS, maximum. I reset the router, the switch, and the PC. The first speed test returned 900 Mbps. Amazing!
Then a second speed test happened within a minute, still 92 Mbps.
Now it’s getting interesting.
I just assembled a brand new AMD gaming rig. It includes an Asus x870 Plus with Wi-Fi, an AMD 9800X3d, and an Asus Prime 5070ti. Everything is functioning properly. The first speed test came back at 92 Mbps. I reset the router and switch again. The speed test improved to 1.2 Gbps.
Then another speed test followed, still 92 Mbps.
What’s happening? All drivers are up-to-date today. I confirmed the cable is correctly placed on the Xfinity gateway and that the DMZ is set.
Help me ObiWan Kenobi...
I've experimented with a few solutions. Resetting just the switch worked. The gateway itself... When I cut the cable from the back of the Gateway, the speed test after reconnecting drops to 1.5Gigs, and then it slows further on subsequent tests.
When network speeds hover just above 90mbps, it usually indicates a faulty cable. This is the speed you expect from a 100mbps connection when accounting for extra data usage. It would be better if Ethernet cables simply stopped working entirely when damaged, but more often they become inconsistent, fluctuating in performance. Likely, a small loss of conductivity or a crack exists at one end. When you reposition it, it reconnects and then, possibly due to temperature shifts or other factors, it drops back to 100mbps later. For longer cables, replacing the damaged section is often practical, though purchasing a new one is usually straightforward. Stick with CAT5E; if possible, opt for CAT6 at a lower cost. The essential requirement is pure copper wire with a size of 22-24 AWG. Many counterfeit products exist, especially flat ones, which fail to meet quality standards. If you don’t notice these details when buying from another seller, it’s worth checking the product specifications. Legitimate sellers are aware of fake cables and typically provide clear information about wire dimensions. I’ve personally observed such flat cables being sold at Walmart, showing that even major retailers are involved in distributing these substandard items.
Curious about the details?
Which model of Xfinity Gateway is being used?
What type of switch is involved?
Are you performing a factory reset on the router or just adjusting settings with admin privileges?
Typically, switches are unmanaged and don’t require changes or resets.
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According to @bill001g, the cables might be the problem, but there could be other factors.
Can you clarify the actual connection path? For example:
ISP (coax, DSL, fiber) → Xfinity Gateway [LAN Port 1] → Router [LAN Port] → LAN ports → wired network devices, then Router → Wireless devices.
Feel free to adjust your diagram to reflect your setup.
If the Xfinity Gateway isn't working, it's probably because your ISP is throttling your connection. Look into your ISP's portal for the total bandwidth consumed during this billing period or contact them to find out about any soft caps they might have in place.
Thank you everyone. I am thinking it's a cable because every time I play with the connection at the Xfinity Gateway it speeds back up. I did a speed test last night after simply disconnecting and reconnecting the cable to the same port and I got 1.5 GB's down. This morning it was the same. And as
@bill001g
stated, this is a flat Cat6 cable that is a few years old now so I wouldn't be surprised if it's time to replace with a better high quality one.
ISP COAX to XFinity Gateway... speeds remain stable on wireless devices and the gateway itself within the 800-1.5 range. The only inconsistency lies in this hardwired connection. From the Gateway (50ft Cat6) to the Linksys 10G powered switch, then 25ft of Cat6 cable to the PC. The 50ft Cat6A from the Gateway to the Switch acts as a weak link. Amazon flat wire is used there. The 25ft from the switch to the PC uses Insignia Cat6A. I will replace the 50ft cable today.
The flat wire has been replaced, but I remain uncertain about the router's connection point. Even with the flat cable, issues could arise if two routers are involved and they both assign DHCP IP addresses to network devices. Are "Gateway" and "router" being used as synonyms for a single device, such as the Xfinity Gateway? It’s not harmful to check this.
The ISPs coax enters the home via their supplied XB8 Gateway (their common term). This device also functions as the router. It’s a dual unit. From the back of the router, we utilize the dedicated 10GB port that connects to a new 10GB switch, which is quite recent—under a year old. Taking the switch off the line and linking directly to the PC doesn’t alter the irregular outcomes, indicating the switch isn’t the issue.
Observing that we occasionally encounter 1.5gb speeds (since we only pay for 2gb down, I’m content with 1.5) and other times only 100mb or less after adjusting the cable, suggests the problem may lie with the cable, connector, or perhaps the gateway itself. Switching to a different cable allows us to confirm whether the fault was with the cable or if further troubleshooting of the gateway is needed, followed by replacing it with a new one from our ISP.
👍 It seems the issue is becoming more specific, so keep checking the ISP coax cables and their accessories. Watch for damage such as corrosion, animal bites, twisted or pinched wires, nail marks, cuts, and scrapes. Stay safe—don’t climb onto roofs or poles.
The ISP should verify signal loss and examine the coax cables too. But it’s simpler to provide a new gateway/router instead of handling repairs yourself.
Hopefully, the replacement resolves the problem.
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