One Bad Cable Spoils the Bunch

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Spoiler Alert!: well, the headline is the spoiler, so the alert is too late!

But, there is a lengthy sub-plot here which has nothing to do with that cable, so aside from documenting the cable saga (which you know the ending of), there was more sleuthing necessary.

I’ve been a Verizon FiOS customer for roughly 18 years, in three different locations (two are still active). I’ve been very satisfied with the service throughout, in all of the locations. If there was anything to complain about, it’s purely the price (and the nickle and diming of fees and services/rentals), but still, I stick with it because it’s been rock solid and fast (and symmetrical download/upload speeds).

In the house (my primary residence) I have gigabit service. In the other active (remote) location, I have the lowest level of service, 300Mbps (which is plenty, and would likely even satisfy me in the house, but I’m not downgrading).

When I first got FiOS I rented their original, ancient, Actiontec router. After a few years, I upgraded to the G1100 router. I later bought my own G1100 router. When I sold that house and moved into the current one, I signed up for gigabit service and used the G1100 router that I already owned.

In the remote location, I originally only had the choice of cable (Time Warner, later rebranded to Spectrum). When FiOS became available there, I instantly swapped (perhaps 6-7 years ago). I also bought a G1100 router knowing I didn’t want to pay rental fees (new FiOS plans include a nice router in the price, so even if you don’t take it, you don’t save money…).

Nine months ago, I upgraded the house router to a G3100 model (to get WiFi 6) and I added two E3200 extenders (connected via coax/moca) to give the whole house great WiFi coverage. I have been delighted with the upgrade, so two months ago, I did exactly the same upgrade in the remote location.

Now we’re all up to speed on how things were as of a few weeks ago. Both locations were outfitted identically (except for the speed of the connection). Both were operating at full capacity (I was getting 980Mbps speed in the house, and 320Mbps speed in the remote location, consistently!).

For safety and sanity, I regularly backup to multiple locations. I pay for two different cloud backup services and backup to each daily. I backup to a local hard drive a few times a month (simply to be able to restore more quickly in an emergency, as both of our laptops turned 9 years old this month!). Finally (and this is the point of this paragraph), I backup certain files (a small percentage) between the house and the remote location (in both directions).

For as long as I’ve had FiOS in the remote location, I’ve consistently experienced full saturation (that’s a good thing) on the link, when copying files in either direction. In other words, if I’m copying 10GBs of data, I will get a full 300Mbps connection (the remote location is the choke point). This is all traveling on Verizon’s internal network, so I never really see a slowdown in speed.

A couple of weeks ago, I started noticing that my speed seemed capped at 100Mbps. But, that wasn’t just to the remote network. If I ran a speed test from certain machines, they too were capped at 100Mbps. But, other speed tests (I will elaborate shortly) showed much higher numbers, so it didn’t feel like there was an issue with the fiber side of the FiOS connection. Still, something was very wrong.

On the other hand, 100Mbps is plenty fast to get normal things done, even if my transfers between locations were ? as fast… I had a ton of other things to work on, so even though this really bugged me (more than you could know), I didn’t even try to figure it out until today (hence this post). That’s not to say that I didn’t think about it a lot (typically laying in bed late at night or early in the morning), but I didn’t investigate the possible cause other than in my mind…

Of course, I had to think about what changed in the past couple of weeks in the house (nothing changed in the remote location). The biggest (perhaps only) change was a new switch. I had been running on an 8-port 1Gbps TP-Link switch for years. It was rock solid. I recently replaced it with a 16-Port 1Gbps Tenda switch which I ordered from China via AliExpress. I couldn’t imagine it was that switch, but hey, it almost had to be.

I didn’t (yet) need 16 ports. I upgraded because (as I’ve mentioned in a recent post) I am in the process of working on many tech projects, and some of them require new/additional network connections. I wanted to be ready to deploy them in advance. Since I only have 7 active connections on that switch at the moment, swapping back to the TP-Link should prove whether the new switch is the issue. Like I said, I’ve been busy with other projects, and I didn’t take the time to do that, since everything was working (for some definition of working).

I have a number of servers in the house (a few physical, and one VM). They can transfer data at full network speed between them (they are all connected to the same switch) which is the main reason I procrastinated swapping switches. While it could have been the new switch, it didn’t feel like it was the new switch, unless it had a single bad port…

I said above that I would elaborate on the FiOS speed issue. My laptop connects to the router via WiFi. When I ran a speed test on the laptop, I was getting much higher speeds than on the servers. The laptop isn’t connected to the switch (obviously), so that pointed to the switch being the issue, and not the FiOS connection.

For the past few days (not as long as the above-mentioned issue was occurring) even my laptop speed has seemed to slow down and be capped at 100Mbps. That was really odd. It also now meant that the problem escalated to the top of my priorities. Not that I can’t live with 100Mbps on the laptop, but it was consuming way too much of my offline thoughts…

I decided that I needed to attack the slow WiFi speed first, as that clearly has nothing to do with the switch! This is the start of the sub-plot, which has nothing to do with the title of this post…

I connected an Ethernet cable to the laptop, and my speed was back to normal. OK, it’s a WiFi, not a FiOS problem, though it could be a router problem, since that provides the WiFi signal. I ran a Verizon trouble-shooting test on their website and it reported that nothing was wrong with the connection (as I suspected).

I checked my WiFi connection and saw that I was connected to the 2.4Ghz band. I can’t remember the last time that happened. I logged into the router, and while everything was turned on (all the bands), it didn’t seem that anything was flowing through the two 5Ghz bands.

I’m running with SON (Verizon’s Self Organizing Network). Basically, it’s their version of mesh and band steering. A device only needs to know a single SSID for WiFi, and the router plus extenders will automatically connect the device to the best choice of band (2.4Ghz or one of the two 5Ghz channels) and the best connection (the main router or one of the two extenders). For the nine months that I’ve had the G3100 in the house (and two months in the remote location) I’ve never had the slightest problem (or even temporary glitch) with SON. I’ve read horror stories on Reddit about issues with SON, but I’ve been lucky (or blessed) to never have experienced them.

Somehow, I assumed that my SON configuration failed. All of my devices were being steered to the 2.4Ghz band. I checked my phone, and sure enough, it too was connected to 2.4Ghz.

Without thinking how that could have happened, I decided to take the advice that Redditors give anyone who complains about WiFi issues, and disable SON. I thought I might turn it back on later, but at least I’d be able to prove whether I could connect to a 5Ghz band, since it would now have a unique SSID.

I left the 2.4Ghz band with the same name that the SON network had, so that IoT devices or anything that only operates on that band (security cameras, etc.) wouldn’t have to be touched. I created two separate  5Ghz SSIDs for the devices that are easy to update (laptops, phones, streaming sticks, etc.).

Sure enough, I was instantly able to access either 5Ghz channel, and got speed test results of nearly 700Mbps over WiFi (like it used to be!). I figured there might have been a firmware upgrade in the past few days that screwed up SON. But, while typing this, I realize there is a more likely culprit (though a firmware upgrade is still a possible issue).

My most recent post (before this one) was about a full power outage in the house on Saturday morning. I now realize that the WiFi speed issues (SON related) all started when the power came back on (though I had so many other things to deal with that I didn’t really notice for another couple of days!).

It’s possible that simply rebooting the router (though I could swear it was rebooted once after the power outage), or just turning SON back on now that it was turned off first, would make it work. But, after reading so many Reddit posts in the past explaining why SON wasn’t necessary (I had assumed, as many others did, that it was necessary for seamless roaming in the house). I can now confirm that this advice was accurate. My phone still switches quickly to the best extender when I move rooms. So, without SON, I can better control which device connects to which band.

OK, done with the sub-plot. Having solved that issue, I was emboldened to tackle the switch. I swapped out the Tenda switch and replaced it with the original TP-Link switch. The problem persisted (still capped at 100Mbps). Aha, it wasn’t the switch (as I had suspected!). And yet, the problem only started after I swapped in the Tenda in the first place!

That left a single possibility. The cable that connected the router LAN port to the switch had to be bad. It wasn’t bad (in that it didn’t work at all), but rather bad in the sense that it was capped at 100Mbps (like an ancient Ethernet cable would be). Now it all became obvious (and easy to test).

When I originally powered on the Tenda switch, the first thing I did was connect it to the TP-Link switch. That way, I could move a single cable at a time from the TP-Link to the Tenda, and only lose connectivity for the few seconds it took to move the cable. Once I proved that this worked fine, I moved all of the cables over, disconnecting the cable that connected the two switches, and putting the TP-Link switch away.

Then I went about choosing the best of the cables that I had (the ones labeled Cat 5e) and took what looked like the best of them (right length, no kinks, cleaner which made me think newer, etc.). I connected that from the router to one of the two uplink ports on the Tenda. All seemed fine. It was only later on (probably the next morning, when manually copying files between the networks) that I realized my speed was capped (on any device connected to the switch!).

Well, as the title already spoiled, the best cable was bad. When I swapped it for another Cat 5e cable, connecting the router to the switch, everything went back to normal. Full 300Mbps between my FiOS networks. 980Mbps speeds from wired connections to the Internet, and 700Mbps WiFi connections (which had nothing to do with the switch or cable). I tested all of the other cables in the switch individually, and they all support full gigabit throughput. Still, for safety sake, I ordered a 10-pack of Cat 6 cables that will be here tomorrow.



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