Modem and Router Slowness Question

NickB · August 20, 2019

I have the Arris SURFboard 32 x 8 DOCSIS 3.0 Modem with the NETGEAR XR300 Gaming Router and all that is plugged into the coax. We have a plan for gigabit and are only getting 50mb over wifi and 500 over ethernet.

We had someone come down from Comcast and they said they couldn't find the issue and just assumed we didn't have a good modem. Is this possible? Could the modem not be compatible with the router?

Thanks!

Eigenvektor · August 20, 2019

There can be lots of different sources:

1. Your modem needs to support Gigabit
2. Your router needs to support Gigabit
3. Your cables need to support Gigabit (Cat 5e or better)
4. Your cables need to be in good shape (e.g. no hard bends)
5. Your computer's NIC needs to support Gigabit
6. Your Wi-Fi needs to support Gigabit (e.g. 802.11g can only to 54 Mbit)

Take a computer/laptop and connect it directly to the modem. Make sure the computer has a (good) NIC that supports at least Gigabit ethernet. Make sure you use a short cable with no hard bends. Now run some speed tests. If you get full speed, your modem shouldn't be the issue.

Next, connect your router to the modem and plug your computer directly into the router. Run the same speed tests again. If you still get full bandwidth, the router isn't the issue. You can then try to plug your computer to the different cables in your house and see if the results change. If so, then that particular cable is probably damaged or bent too much.

For Wi-Fi, both your router and your client need to have 802.11ac (aka Wi-Fi 5) or better. Otherwise you'll not be getting Gigabit over Wi-Fi (You'll probably never get full bandwidth over Wi-Fi, depending on how many Wi-Fi clients there are at the same time).

Donut417 · August 20, 2019

7 hours ago, NickB said:

I have the Arris SURFboard 32 x 8 DOCSIS 3.0 Modem with the NETGEAR XR300 Gaming Router and all that is plugged into the coax. We have a plan for gigabit and are only getting 50mb over wifi and 500 over ethernet.

We had someone come down from Comcast and they said they couldn't find the issue and just assumed we didn't have a good modem. Is this possible? Could the modem not be compatible with the router?

Thanks!

That modem is not rated for Gigabit on the Comcast network. You need a Docsis 3.1 modem. Dont try to argue this fact because Comcast will tell you to pound sand. They will never give you Gigabit on that modem period. Also the 32 channel Docsis 3.0 modems use the Puma 6 chip that is known to have issues. So much so Arris is getting sued over the SB6190, over Intel mistake.

From my understanding all Docsis 3.1 modems are pretty safe and all use broadcom chips.