Wits end: trying to get 1+ Gbps realized at PC using Xfinity 1.2Gbps Plan (Provisioned 1.44Gbps)

I am tired of researching and failing. This unit was one of my last attempts.

Comcast tech was out to the house and measured 1.3Gbps down to modem.

  • Link aggregation activated on Arris SB8200 modem
  • (2) CAT6 cables connecting both ports on SB8200 to WAN and LAN4 on Asus RT-AX86U router
  • WAN aggregation enabled and shows active on landing page of router
  • CAT6 cable from 2.5Gbps port on RT-AX86U to Plugable 2.5Gbps Ethernet Adapter
  • Plugable 2.5Gbps Ethernet Adapter plugged into USB-C on ASUS Z270E ROG Strix motherboard
  • USB-C port is confirmed running at “SuperSpeed” (3.1, 5 Gbps) using Windows USBView
  • Windows 11 on PC
  • Device Manager and Windows Task Manger returns Plugable/Realtek adapter is active and network connection confirmed at 2.5Gbps speed

Ookla returns 450Mbps download speed: effectively half my known speed. Taking Plugable adapter out of equation, all other arrangements the same, except for plugging directly into built-in 1Gbps ethernet on-board, Ookla returns 850-950Mbps.

Someone, please HELP!!!


I sent a response to your support ticket a short time ago.

Just to note it here as well, for others who may find this post, a common misconception about link aggregation is the idea that it will allow for transfer rates equal to the aggregated connections to a single PC.

Link aggregation (802.3ad) does not allow a single client to exceed the performance of one of the aggregated links, rather, it helps to balance load between multiple clients.

For example, in this configuration, two clients that were operating at full capacity could theoretically get about 600Mbps each, resulting in a combined total of 1.2Gbps. This doesn’t take into account network overhead, which usually takes about 5%-20% off that figure.

Since the maximum throughput of each of the aggregated connection links is 1Gbps, no single client can exceed 1Gbps.

In order to possibly see speeds in excess of 1Gbps on a single client through your ISP, you would need a modem that has a 2.5Gbps or higher Ethernet port, a router with a 2.5Gbps or higher WAN port and LAN port, and then a 2.5Gbps or higher Ethernet adapter on your client PC.

With regards to testing the performance of the adapter, going through an Internet speed test is not the way to do it. There are too many variables to account for. A site like speedtest.net (Ookla), will end up getting different routes to the server each time it is run, and will usually get different servers between runs.

Rather, it should be tested as a point-to-point link as described in our knowledge base article here: https://kb.plugable.com/network-adapters/understanding-and-troubleshooting-network-performance

I would also make sure that your OS, and drivers for the adapter, are up-to-date.

I look forward to assisting you further in your open support case.

Thank you.

Andy - thanks for the quick and thorough response. I found my bottleneck: it was the SB8200 modem. While it is capable of “10+ Gbps speeds”, this is a combined throughput across all clients. No single client will exceed 1Gbps - ever.

I have switched to the Comcast/Xfinity XFi platform for unlimited data and am now using the XB7 gateway.

With my current setup, using the Plugable adapter, I was able to achieve a real-world, point of service Ookla speed of 1440Mbps (which is 1.2Gbps x 20% overprovisioning).

I will leave a positive review for both the product and your customer service on Amazon.


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Hi Ryan,

Thanks for reporting back, and for taking the time for a review!

If you need further assistance with the adapter, please feel free to contact us again. We’re happy to help!

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