Overloaded C3000-100NAS?

[lstone19]

Problem: Two or three times a day for short periods of usually no more than 15 minutes, we are unable to connect to the Internet (Comcast). When it happens, all devices on the network are affected. It seems to have become worse since my wife and son started working from home so more VPN, Zoom, etc. Oddly, when it happens, the unreachable destinations can be pinged but no http, https, imap, or smtps so I'm thinking it's just TCP but not UDP connections that are affected. Also, it appears most already established connections (e.g. VPN, some complex HTTP such as Facebook) are maintained so guessing it has to do with establishing connections, not maintaining them.

Provider: Comcast

Router: Netgear C3000-100NAS Firmware V2.02.22 (latest for Comcast per Netgear KB)

Other Network: Router connects to Netgear WAC124 (in bridge mode as WAP), then to a 16-port Netgear switch (in basement as wired hub for the house). From the 16-port switch are various other switches and two Netgear WAC104 WAPs (big house so three WAPs). All switches, etc. are Gigabit (recently upgraded from mostly 100Mbps).

More thoughts: I started thinking this was a Comcast problem but now have started increasingly thinking it may be a resource exhaustion issue on the router. The router has been working fine for 4+ years (one of the few Gigabit devices before my recent upgrade) but it's getting pushed more. Despite having done some professional network management earlier in my career, I just don't have the tools at home for digging deep into this.

Could I be on the right track thinking it could be a resource exhaustion issue in the router? As currently wired, I could switch the C3000 to bridge mode and make the WAC124 the router if someone thinks that's worth trying (just need to find the time I can interrupt everyone).

[lstone19 · Accepted solution]

It's been a week since putting the C3000 in bridge mode and making my new WAC124 the router and no recurrences of the outages I've been seeing. Also five days since replacing the powered splitter with an unpowered one which has brought the power levels down to the range plemans said it should be (seeing about 5 dBmV on each download channel).

My conclusion, largely from another forum where I posted the issue, is that C3000 has too small a NAT table which was becoming exhausted under high demand. It would appear the WAC124 has a larger one (unfortunately, I could not find spec sheets for either listing the size). 

I'm considering this issue resolved.

[plemans]

What speeds do you pay for?

What speeds do you get hardwired to the router?

If you log into the C3000 and take a screen snip of the cable connection page and the logs, that can help. 

[lstone19]

I believe (Comcast doesn't make it easy) I am paying for 150Mbps down / who knows up. Despite that, a recent speed test from a wired computer game me 233 Mbps down and 12 Mbps up while my Wi-Fi connected laptop showed 120 Mbps down and 11 Mbps up.

Screenshots of the cable connection page, log, and event log are attached.

[plemans]

power levels are a bit high. Optimal is between -7dbmv and 7dbmv. You're in the upper range of stable. But not seeing errors.
Maybe the power level is going up a bit at times and causing issues. I'd try an attenuator or you can try a splitter in line to see if it drops the level and keeps it more stable.

[lstone19]

Interesting. I have a powered splitter to split the cable to the modem and to a TiVo. I'll try replacing it with a non-powered splitter.

Why a powered splitter? Well, while today the cable only serves those two (upstairs TVs servers by TiVo minis via Ethernet), when the cable had to serve upstairs TVs, there were problems due to the long run (length of the house, up to the attic, another splitter, and then back to the master bedroom - probably over 100 feet). Putting a powered splitter both for the run to the attic and another in the attic cleared up the TV reception problems.

[plemans]

try this. 

get a double splitter. 

Send one leg to the modem. Send the other to the powered splitter. and then feed the rest of the home.

You don't want a powered splitter prior to the modem. 

[lstone19]

Just an update to let you know I'm not ignoring the suggestion. I found the unpowered splitters I had were not suitable for today's needs so am working on getting a new one. In the meantime, based on a response in another (non-Netgear) forum where I posted this, I have gone ahead and reconfigured to put the C3000 in bridge mode and make the WAC124 the router. I want to give it a few days like that before making another change.

While getting the power levels in spec is certainly important, I don't think it's the problem. I'm fairly convinced that the problem is only with new TCP connections and not with UDP or existing TCP connections and from my days doing system administration on various computer systems, most "existing works, new fails" type problems are resource exhaustion issues (I've worked on systems where if you saw something hung in a Resource Wait state, your next step was to start asking when you could reboot the system). If the power levels were the problem, I'd expect everything to fail, not just new.

[plemans]

You're welcome to try whatever you think is going to work.
I would try and get the powered splitter feeding the modem out of there. It can give you to high of numbers as well as cause issues on the upload.

[lstone19 · Accepted solution]

It's been a week since putting the C3000 in bridge mode and making my new WAC124 the router and no recurrences of the outages I've been seeing. Also five days since replacing the powered splitter with an unpowered one which has brought the power levels down to the range plemans said it should be (seeing about 5 dBmV on each download channel).

My conclusion, largely from another forum where I posted the issue, is that C3000 has too small a NAT table which was becoming exhausted under high demand. It would appear the WAC124 has a larger one (unfortunately, I could not find spec sheets for either listing the size). 

I'm considering this issue resolved.