Question only getting 25% speed of internet I pay for (Gigabit Comcast cable)

[bigcletus]

I have Comcast Gigabit internet plan, but I have never gotten that speed. I use my own Motorola DCSIS 3.0 modem and an Asus RT-AC68R/U router running TomatoUSB custom software. My speeds are 240 Mbps down and 24 Mbps up consistently on my ethernet (cat5e) connected PC that is in my office. Wifi connected devices are usually half of that. This is frustrating considering paying for 1000mbps down and only getting 25% of the speed.

Things I have tried include connecting laptop directly to the modem, bypassing the router and the best speed I could get was 500mbps after several speed tests. Plugging the laptop directly into the router resulted in the usual 240-280 Mbps.

I realize that Docsis 3.1 is needed for 1gbps, but Docis 3.0 should give 800-900 mbps . I recently purchased a new Nighthawk wifi6 cable modem router combo from Costco thinking my existing hardware was the bottleneck. To my surprise, I was getting the same speeds, even thought the new router was Docsis 3.1. I ended up returning it and putting things back the way they were as there was no benefit with the Nighthawk, not to mention I was getting lots of connection drops using it. I was not impressed at all with that router.

I am looking for any suggestions or advice as to what the issue could be with these slow speeds. Any help is greatly appreciated.

 

[rgd1101]

what the motorola modem?

 

[Aeacus]

This is frustrating considering paying for 1000mbps down and only getting 25% of the speed.

Read your contract with your ISP again. Since i'm pretty sure it says "up to 1000 Mbps" rather than "minimum of 1000 Mbps" or "constant 1000 Mbps".
Contract might also say what the average speed is.

 

[bill001g]

Not sure why it does not work better connected directly to the modem. Almost seems like the ISP has the account setup wrong if it only runs 500mbps.

Your 240mbps problem is likely because you are running tomato on the router. Modern routers use a hardware NAT offload feature so the CPU is not burdened by the nat. There are license issues trying to use this feature with third party firmware which means the CPU chip must do all the NAT.
You many times will not get much over 300mbps even on the most powerful routers.

I think you can still get merlin images for that router. Merlin is somewhat simpler than other third party firmware but it has many of the features. Key is they work with asus and can use the asus NAT acceleration drivers.

 

[gggplaya]

I haven't been impressed with Netgear in the last few years. I just had a coworker with a netgear modem and netgear router. Both advertised to get gigabit speed. He also couldn't get gigabit speeds with the combo. So he swapped out to a Motorola Modem and it solved his issue. We both thought it was weird we couldn't hit gigabit speed with a Netgear-Netgear combo. I haven't recommended any Netger product in years, aside from a simple $15 network unmanaged switch. Their software team isn't what it used to be.

Comcast has profiles for all approved modems, they were not able to provision my Docsis 3.0 modem for gigabit speed, best I would get was 300mbps. I bought a Motorola MB8600 Dociss 3.1 modem and it solved the issue, instant gigabit speed. Though they have the MB8611 now, which has an actual 2.5gbe port.

Also, you shouldn't run Tomato firmware anymore. It's no longer updated. So security is an issue. As BILLG said, get MERLIN firmware for Asus routers. Merlin takes the published Asus firmware and brings in newer OpenWRT libraries. It's completely up to to date and far more reliable, plus has hardware NAT.

 

[bigcletus]

The cable modem is a Motorola MB7621 24x8 channel

Not sure why it does not work better connected directly to the modem. Almost seems like the ISP has the account setup wrong if it only runs 500mbps.

Your 240mbps problem is likely because you are running tomato on the router. Modern routers use a hardware NAT offload feature so the CPU is not burdened by the nat. There are license issues trying to use this feature with third party firmware which means the CPU chip must do all the NAT.
You many times will not get much over 300mbps even on the most powerful routers.

I think you can still get merlin images for that router. Merlin is somewhat simpler than other third party firmware but it has many of the features. Key is they work with asus and can use the asus NAT acceleration drivers.

Hmmm...I was getting the same speeds with the stock Asus/T-mobile firmware prior to trying the Tomato custom firmware.

Also, I only get internet from Comcast, so the line from the street goes directly into the smart box in house closet then directly into modem, there are no splitters or anything else to draw off the incoming signal before it hits the modem. Thanks for the help.

 

[gggplaya]

The cable modem is a Motorola MB7621 24x8 channel



Hmmm...I was getting the same speeds with the stock Asus/T-mobile firmware prior to trying the Tomato custom firmware.

Also, I only get internet from Comcast, so the line from the street goes directly into the smart box in house closet then directly into modem, there are no splitters or anything else to draw off the incoming signal before it hits the modem. Thanks for the help.

Motorola website describes the speeds for that modem as only good for Comcast's 300mbps and 400mbps plans: https://www.motorola.com/us/mb7621/p

I don't think Comcast will have a profile for that modem which will get you the full potential out of it. The modem may be capable of 24 downstream lanes, but that doesn't mean Comcast can give you 24 downstream lanes, they might only give you 12 etc....

I would upgrade to a good DOCSIS 3.1 Modem if you have a gigabit plan.

 

[bigcletus]

Motorola website describes the speeds for that modem as only good for Comcast's 300mbps and 400mbps plans: https://www.motorola.com/us/mb7621/p

I don't think Comcast will have a profile for that modem which will get you the full potential out of it. The modem may be capable of 24 downstream lanes, but that doesn't mean Comcast can give you 24 downstream lanes, they might only give you 12 etc....

I would upgrade to a good DOCSIS 3.1 Modem if you have a gigabit plan.

Any recommendations on a good docsis 3.1 modem/router that isn't too expensive?

 

[gggplaya]

Any recommendations on a good docsis 3.1 modem/router that isn't too expensive?

I'm not a fan of combo units. Wifi protocols tend to update far quicker than cable protocols. Docsis 3.1 is capable of 10gbps, so we'll be on that for a while. Whereas people are still adopting wifi 6E and they're already soon to launch Wifi 7 by the end of this year. Wifi 7 will give significantly more bandwidth with 320mhz channel width and is targeted towards using VR googles without wires at full resolution.

For a modem, I'd recommend Motorola MB8600 or MB8611. They've been solid for everyone I've recommended them to. I've been using the MB8600 for years now, and it hasn't skipped a beat. I don't know how good or bad their combo unit is.

 

[BFG-9000]

If your current DOCSIS 3.0 modem has only 4 or 8 download streams then maybe it really is only good to 500Mbps sometimes on Comcast's network because that's oversubscribed. It might be able to go faster in the middle of the night.

I would strongly suggest a DOCSIS 3.1 modem like the mentioned 32-stream MB8600 because those all have PIE which is really pretty impressive--you can get a <30ms ping under load and therefore an "A" bufferbloat score on all those speedtest sites even without any QoS in your router.

Of course with some tinkering with cake QoS you could get to 5ms and thus "A+" but this takes some CPU to do in software and the 800MHz ARM CPU in your RT-AC68 only has enough power to run this up to 93Mbps.

The latest FreshTomato (the currently supported fork of Tomato) 2023.1 is only 3 days old so I'd guess it's as current as can be. And it supports NAT acceleration/hardware offloading just like stock firmware so long as CTF & FA options are selected (which just like stock prevents QoS from working properly as some of the NAT work is then done in the switch chip instead of the CPU)

I'd suggest the SmallNetBuilder WAN-to-LAN router charts for routers that can move gigabit speeds without QoS. With early firmware your RT-AC68 tested at 754.5Mbps however note the Netgear R7000 which has the same chipset and all the same hardware except the CPU is clocked to 1000MHz can rout full gigabit wire speeds at 931.4Mbps. You can overclock your router to 1000MHz in Tomato using commandline under Tools--System Commands and I have never seen one not run at 1000MHz (the R7000 is much larger with a more substantial heatsink though so don't put it someplace hot). Just something to try before buying new hardware.

I would also recommend against modem/router combo devices because you cannot flash firmware to the router side of those, so you are stuck with stock--and not even the latest stock but whatever the cable company decides to push to it. So you could be stuck with security vulnerabilities while Comcast is happy to stay with an older version to avoid validation hassles. And of course then Comcast broadcasts a free open xfinitywifi Guest Wifi hotspot from your modem to any Comcast subscriber. I don't like to buy devices I cannot control.

 

[kerberos_20]

If your current DOCSIS 3.0 modem has only 4 or 8 download streams then maybe it really is only good to 500Mbps sometimes on Comcast's network because it's oversubscribed. It might be able to go faster in the middle of the night.

its probably from modem side, modem has 24/8 stream lanes which should run 900Mbit+ plans just fine, but in real life its barely enough for up to 400Mbit plans
32/8 modem good enough for 500Mbit

for gigabit+ docsis 3.1 is required (for most usa internet providers)