Cable Modem Recommendation

Stugots

Supreme [H]ardness
Joined
Feb 25, 2004
Messages
7,234
I recently upgraded from 400mbit to 800mbit on my xfinity service and it looks like my tried and true Arris SB6183 is finally in need of an upgrade to take advantage of the new speed. Does anyone have any good recommendations for a replacement modem?

I'm looking for a straight modem, no wifi/router built-in. Some options I was looking at:

Arris SB8200
Arris S33
Motorola MB8600 / MB8611
 
I know the 8200 and s33 seem to be pretty solid. I'm a believer in getting only what you need, so I'd find a used 8200 for cheap and be done with it.
 
I would like a small amount of future proofing, so I'm kinda leaning towards the S33 because it has 2.5G LAN port.
You can do that as well.

A lot of people spent $200 on the 8200 when it came out to 'future proof' because it was going to be able to aggregate both ethernet ports for >1Gb speeds. Well, that never happened and then the s33 came out with the 2.5Gb port and most providers are just barely over 1Gb, and even that's not cheap. imo, future proofing today for future isp moves is a waste imo. There was a time, and in certain situations it still makes sense, but for isp equipment it's always big hit and miss since they can also just drop support of a modem 'just because' and then you still have to replace it.
 
Arris is still the go-to in the game. The S33 is currently on sale from Amazon for $164 ("renewed" is $24 less), close to the regular price for the older SB8200. At that price it'll cover rental fees in about a year.

FWIW, my Netgear CM1150V (only 3rd-party option for Comcast voice support when purchased) has been solid for 2.5+ years.

Not sure how the Motorola units stack up anymore, now that they're no longer associated with Arris.
 
I know I've seen a few used sb8200s sold for $25/30 shipped on homelabsales/hardwareswap on reddit. Usually this happens when someone moves and has fibre at their new location and just doesn't want to throw away their perfectly working modem. (y) win-win all around
 
Last edited:
Taking the opportunity to replace and upgrade my PCEngines APU2 firewall too. From what I’m reading I will be pushing its limit with 800mbit.
 
Taking the opportunity to replace and upgrade my PCEngines APU2 firewall too. From what I’m reading I will be pushing its limit with 800mbit.
With a lot of tweaking, I got mine (running PFsense) to cap out at just under 800mbps. Decided it wasn't worth the hassle, and also upgraded to 1.2gbps service, and went with a Mikrotik RB4011iGS+. Been a better experience all around for me.
 
I’ve really enjoyed the APU2, and it’s served me
Well for many years. I wish they had a newer product with more horsepower.
 
I’ve really enjoyed the APU2, and it’s served me
Well for many years. I wish they had a newer product with more horsepower.
The real issue is the single-threaded net stack nature of PFsense, due to the FreeBSD core it's built on.
 
Firewall and Cable Modem replaced, getting only slightly better speeds. Money well spent!

I need to take a closer look at the cables I'm using. I'm wondering if I have an old cat5 instead of cat5e or cat6 cable someplace. Or maybe my coax line is degraded or damaged coming into my house.
 
Firewall and Cable Modem replaced, getting only slightly better speeds. Money well spent!

I need to take a closer look at the cables I'm using. I'm wondering if I have an old cat5 instead of cat5e or cat6 cable someplace. Or maybe my coax line is degraded or damaged coming into my house.

Cat 5 ethernet should still support 1 Gb ethernet, provided all eight conductors were wired up properly. If not, you'd get no better than 100 Mb.

As a test, move your cable modem as close to the demarcation point (where the incoming cable line meets your residence) and test. Basic way to determine if the problem is cable/splitters/etc. in your home or something the provider is responsible for.

You should be able to pull a diagnostic from the cable modem by going to 192.168.100.1 in your browser. It'll look something like this:
Code:
Startup Procedure
Procedure     Status     Comment
Acquire Downstream Channel     507000000 Hz     Locked
Connectivity State     OK     Operational
Boot State     OK     Operational
Security     Enabled     BPI+
IP Provisioning Mode     Honor MDD     honorMdd(4)
 
Downstream Bonded Channels
Channel     Lock Status     Modulation     Channel ID     Frequency     Power     SNR     Correctables     Uncorrectables
1    Locked    QAM256    20    507000000 Hz    -5.2 dBmV    40.5 dB    6931    4
2    Locked    QAM256    17    483000000 Hz    -5.8 dBmV    40.3 dB    7724    11
3    Locked    QAM256    18    489000000 Hz    -5.8 dBmV    40.3 dB    7654    10
4    Locked    QAM256    19    495000000 Hz    -5.4 dBmV    40.5 dB    7533    3
5    Locked    QAM256    21    513000000 Hz    -5.2 dBmV    40.6 dB    6811    7
6    Locked    QAM256    22    519000000 Hz    -5.3 dBmV    40.4 dB    6870    17
7    Locked    QAM256    23    525000000 Hz    -5.7 dBmV    40.4 dB    6682    13
8    Locked    QAM256    24    531000000 Hz    -5.6 dBmV    40.4 dB    6457    4
9    Locked    QAM256    25    537000000 Hz    -5.7 dBmV    40.3 dB    5730    1
10    Locked    QAM256    26    543000000 Hz    -5.6 dBmV    40.3 dB    5598    0
11    Locked    QAM256    27    549000000 Hz    -5.9 dBmV    40.3 dB    5681    0
12    Locked    QAM256    28    555000000 Hz    -6.1 dBmV    40.1 dB    6746    0
13    Locked    QAM256    29    561000000 Hz    -5.9 dBmV    40.1 dB    6913    0
14    Locked    QAM256    30    567000000 Hz    -6.1 dBmV    40.1 dB    7082    0
15    Locked    QAM256    31    573000000 Hz    -5.8 dBmV    40.2 dB    6768    4
16    Locked    QAM256    32    579000000 Hz    -5.8 dBmV    40 dB    6406    0
17    Locked    QAM256    33    585000000 Hz    -5.8 dBmV    40 dB    6669    1
18    Locked    QAM256    34    591000000 Hz    -5.8 dBmV    40 dB    7138    0
19    Locked    QAM256    35    597000000 Hz    -5.9 dBmV    39.9 dB    7270    0
20    Locked    QAM256    36    603000000 Hz    -6 dBmV    39.9 dB    8116    0
21    Locked    QAM256    37    609000000 Hz    -6.1 dBmV    39.9 dB    7665    0
22    Locked    QAM256    38    615000000 Hz    -6.1 dBmV    39.8 dB    7824    0
23    Locked    QAM256    39    621000000 Hz    -6.1 dBmV    39.8 dB    8348    0
24    Locked    QAM256    40    627000000 Hz    -5.9 dBmV    40 dB    7328    0
25    Locked    QAM256    41    633000000 Hz    -5.9 dBmV    39.9 dB    7282    0
26    Locked    QAM256    42    639000000 Hz    -5.7 dBmV    39.9 dB    6963    0
27    Locked    QAM256    43    645000000 Hz    -5.5 dBmV    39.9 dB    6957    0
28    Locked    QAM256    44    651000000 Hz    -5.6 dBmV    39.8 dB    8674    0
29    Locked    QAM256    45    657000000 Hz    -5.6 dBmV    39.7 dB    9570    0
30    Locked    QAM256    46    663000000 Hz    -5.4 dBmV    39.6 dB    9760    0
31    Locked    QAM256    47    669000000 Hz    -5.3 dBmV    39.7 dB    9066    0
32    Not Locked    Unknown    0    0 Hz    0.0 dBmV    0.0 dB    0    0
 
Upstream Bonded Channels
Channel     Lock Status     US Channel Type     Channel ID     Symbol Rate     Frequency     Power
1    Locked    ATDMA    1    2560 Ksym/sec    10400000 Hz    48.8 dBmV
2    Locked    ATDMA    2    5120 Ksym/sec    16400000 Hz    46.3 dBmV
3    Locked    ATDMA    3    5120 Ksym/sec    22800000 Hz    45.8 dBmV
4    Locked    ATDMA    4    5120 Ksym/sec    29200000 Hz    45.8 dBmV
5    Not Locked    Unknown    0    0 Ksym/sec    0 Hz    0.0 dBmV
6    Not Locked    Unknown    0    0 Ksym/sec    0 Hz    0.0 dBmV
7    Not Locked    Unknown    0    0 Ksym/sec    0 Hz    0.0 dBmV
8    Not Locked    Unknown    0    0 Ksym/sec    0 Hz    0.0 dBmV
 
Downstream OFDM Channels
Channel     Lock
Status     Modulation /
Profile ID     Channel
ID     Frequency     Power     SNR /
MER     Active Subcarrier
Number Range     Unerrored
Codewords     Correctable
Codewords     Uncorrectable
Codewords
1    Locked    0 ,1 ,2 ,3    48    850000000 Hz    -8.3 dBmV    38.8 dB    1108 ~ 2987    44185217202    35264763369    530352
2    Not Locked    0    0    0 Hz    0 dBmV    0.0 dB    0 ~ 4095    0    0    0
 
Upstream OFDMA Channels
Channel     Lock Status     Modulation / Profile ID     Channel ID     Frequency     Power
1    Not Locked    0    0    0 Hz    0 dBmV
2    Not Locked    0    0    0 Hz    0 dBmV
 
Current System Time:Mon Nov 07 13:07:52 2022
System Up Time:20 days 11:59:54
 
Funny...I was just looking at that. I can see a fair amount of uncorrectable errors on a number of channels.
 
Startup Procedure
ProcedureStatusComment
Acquire Downstream Channel507000000 HzLocked
Connectivity StateOKOperational
Boot StateOKOperational
Configuration FileOK
SecurityEnabledBPI+
DOCSIS Network Access EnabledAllowed

Downstream Bonded Channels
Channel IDLock StatusModulationFrequencyPowerSNR/MERCorrectedUncorrectables
5LockedQAM256507000000 Hz0.4 dBmV42.0 dB376578
2LockedQAM256489000000 Hz-0.3 dBmV41.9 dB34638
3LockedQAM256495000000 Hz0.1 dBmV42.0 dB312325
4LockedQAM256501000000 Hz0.9 dBmV42.2 dB770
6LockedQAM256513000000 Hz0.6 dBmV41.8 dB2150
7LockedQAM256519000000 Hz0.0 dBmV41.7 dB3410
8LockedQAM256525000000 Hz-0.4 dBmV41.7 dB3589
9LockedQAM256531000000 Hz0.7 dBmV42.1 dB414438
10LockedQAM256537000000 Hz-0.8 dBmV41.7 dB2682
11LockedQAM256543000000 Hz-1.9 dBmV40.8 dB405757
12LockedQAM256549000000 Hz-4.2 dBmV39.8 dB56291
13LockedQAM256555000000 Hz-2.6 dBmV40.6 dB360340
14LockedQAM256561000000 Hz-1.4 dBmV41.3 dB4050
15LockedQAM256567000000 Hz0.3 dBmV41.6 dB5031213
16LockedQAM256573000000 Hz0.5 dBmV41.9 dB2120
17LockedQAM256579000000 Hz0.9 dBmV41.6 dB413443
18LockedQAM256585000000 Hz0.2 dBmV41.3 dB35160
19LockedQAM256591000000 Hz1.1 dBmV41.8 dB2340
20LockedQAM256597000000 Hz0.3 dBmV41.3 dB3270
21LockedQAM256603000000 Hz1.1 dBmV41.7 dB2780
22LockedQAM256609000000 Hz1.4 dBmV41.6 dB2830
23LockedQAM256615000000 Hz1.6 dBmV41.2 dB2440
24LockedQAM256621000000 Hz0.5 dBmV40.9 dB50274
25LockedQAM256627000000 Hz0.4 dBmV41.1 dB3420
26LockedQAM256633000000 Hz-0.7 dBmV40.7 dB4980
27LockedQAM256639000000 Hz0.0 dBmV41.2 dB47148
28LockedQAM256645000000 Hz1.1 dBmV41.3 dB35365
29LockedQAM256651000000 Hz1.1 dBmV40.7 dB3840
30LockedQAM256657000000 Hz1.6 dBmV41.1 dB601347
31LockedQAM256663000000 Hz0.9 dBmV41.0 dB4290
32LockedQAM256669000000 Hz0.6 dBmV41.1 dB42669
37LockedOther690000000 Hz0.3 dBmV38.5 dB19827886566173



Upstream Bonded Channels
ChannelChannel IDLock StatusUS Channel TypeFrequencyWidthPower
14LockedSC-QAM Upstream35600000 Hz6400000 Hz45.0 dBmV
25LockedSC-QAM Upstream29200000 Hz6400000 Hz45.0 dBmV
36LockedSC-QAM Upstream22800000 Hz6400000 Hz45.0 dBmV
47LockedSC-QAM Upstream16400000 Hz6400000 Hz44.0 dBmV
510LockedSC-QAM Upstream39600000 Hz1600000 Hz46.0 dBmV
 
Yeah, that's a lot of errors, especially with whatever is happening on channel 37.

Your power numbers are almost perfect (0 dBmV is optimal, +/- 10, IIRC, is acceptable), and the S/N also looks good.

This looks very similar to an issue I had with a bad coax cable a number of years ago. In that instance all the numbers were good, except it all went to hell on one channel and made the whole thing near-useless.

So yeah, hook it up near the demarc as I suggested up-thread and see how things work.

And if you call the provider about this, don't ever mention "channels". Tier-one reps will insist your talking about WiFi and it's impossible to get them off that script.
 
The real issue is the single-threaded net stack nature of PFsense, due to the FreeBSD core it's built on.

PF in FreeBSD has been multithreaded since 10.0, released Jan 2014. I don't use PFSense, but I'm pretty sure they stay close to upstream FreeBSD, and almost certainly aren't still running FreeBSD 9.

Sometimes people have trouble with PPPoE, but that's because PPPoE is an abomination and also NICs usually will hash all the incoming PPPoE into the same RX queue and then you don't get to multithread inbound packets. Or maybe you have a NIC that only has one queue. Shouldn't have PPPoE on a cable modem, I would really hope, but maybe CenturyLink is running that somewhere.
 
PF in FreeBSD has been multithreaded since 10.0, released Jan 2014. I don't use PFSense, but I'm pretty sure they stay close to upstream FreeBSD, and almost certainly aren't still running FreeBSD 9.

Sometimes people have trouble with PPPoE, but that's because PPPoE is an abomination and also NICs usually will hash all the incoming PPPoE into the same RX queue and then you don't get to multithread inbound packets. Or maybe you have a NIC that only has one queue. Shouldn't have PPPoE on a cable modem, I would really hope, but maybe CenturyLink is running that somewhere.
I'm not talking the base OS or anything, but, last I looked (it has been a couple years, but I think after 10) in the codebase, the network stack wasn't threaded. Well, it was multi-thread aware, but, two (or more) threads would never run in parallel. So on low power systems like an APU2c2, it was a struggle to crack 1Gbps.
Huge +1 to PPPoE being downright trash though (not PFsense's fault, that).
 
I'm not talking the base OS or anything, but, last I looked (it has been a couple years, but I think after 10) in the codebase, the network stack wasn't threaded. Well, it was multi-thread aware, but, two (or more) threads would never run in parallel. So on low power systems like an APU2c2, it was a struggle to crack 1Gbps.
Huge +1 to PPPoE being downright trash though (not PFsense's fault, that).
Well, I don't have a good enough connection where I run pf right now to stress anything, so hard for me to know for sure... But the basic tcp stack is definitely multithreaded, cause I've run it hard and seen 16 cores loaded up with mostly kernel tcp work; that was with ipfw (and nearly no stateful rules) though. You definitely need a NIC that has multiple queues, preferably one per core... A look around says the apu2c2 has intel i211 nics which might only do two queues... Which isn't going to be ideal on a quad core cpu; the i210 on the x4 skus can do four queues which would be a better match.
 
Yeah, that's a lot of errors, especially with whatever is happening on channel 37.
Tons of correctable errors on 37 is normal. It's a DOCSIS 3.1 OFDM channel. OFDM channels send data in much larger chunks, send at a higher bitrate than DOCSIS 3.0/QAM256 channels and use better error correction to deal with the resulting errors. The uncorrectables could be lower, but shouldn't cause much trouble. 6173 / 1982788656 = .0003% uncorrectable at most. Your modem doesn't report total codewords/packets, so it's probably less than 0.0003% since I divided by correctables rather than total.

My OFDM channel looks like this (Comcast, Netgear CM2050V modem, 106 days uptime!):

Downstream OFDM Channels
ChannelLock StatusProfile IDChannel IDFrequencyPowerSNR / MERActive Subcarrier
Number Range
Unerrored
Codewords
Correctable
Codewords
Uncorrectable
Codewords
1Locked0 ,1 ,2 ,3193957000000 Hz2.6 dBmV44.1 dB148 ~ 39472324447294950378662071043
 
This is my SB8200. Sadly this is only with 5 days uptime as I was having internet issues a few days ago that turned out to be 100% DNS based and nothing to do with the modem.
1668135061017.png

I do have an amplifier now, it's set right where my cable hits my house. I have weirdly long cable lines that snake around the outside of my house for whatever unknown reason.
It made a HUGE difference with my correctables/uncorrectables.

https://smile.amazon.com/gp/product/B0792PTCFP/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
 
Thanks. I may give that a try. Found and eliminated an old splitter in the house, didn’t make a difference.
 
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