Degrading My 10-Gigabit Ethernet Link To 5-Gigabit On Purpose!

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It has been about eight weeks since I upgraded to core of my home network. I added a Mokerlink 2.5-gigabit switch to both my network cupboard and my home office on the opposite side of the house. The 5-port switch in my office has a pair of 10-gigabit SFP+ ports, while the 8-port switch in the cupboard has only one. This gives me a nice, fast connection between all the devices in my office and my network cupboard, and a cheap 10-gigabit Ethernet card in my desktop PC has given me a full 10gbe link to the other side of the house.

The specifications for 10-gigabit Ethernet require Cat 6A wiring to reach the full distance, but you can use Cat 5e or Cat 6 depending on the quality of your wiring. I made sure to order a set of three Xicom 10-gigabit SFP+ modules with the hope that they would if I wasn’t be able to negotiate 10 gigabits across the existing Cat 5e wiring.

Testing the limits of my 10 gigabit Ethernet connection

I have to admit that I wasn’t terribly surprised when everything lit up at a solid 10 gigabits per second. I definitely have less than 100’ of cable between my two switches, and that isn’t terribly far!

I was packing up a pouch for my NanoKVM kit with things like flat-pack Ethernet cables and RJ-45 couplers. I have way too many couplers, because I needed two or three but had to buy a 10-pack! I also have plenty of extra 10’ flat-pack cables. I wound up having a fun idea while staring at them.

How many 10’ cables and couplers can I add to this 10-gigabit Ethernet run before it degrades to 5gbe? An even more important question might be whether it will even attempt to connect at 5-gigabits per second!

How about a tl;dr?!

I don’t want to keep you here longer than necessary. There is currently something like 70’ for Cat 5 and Cat 5e cable between my two switches, and they have been happily talking at 10 gigabits per second for months.

That trend continued after adding two 10’ flat-pack Ethernet cables and two RJ-45 couplers to the that chain of wiring. Adding a third 10’ cable and coupler dropped the connection down to 5gbe.

That doesn’t mean that 90’ or 100’ feet is the actual limit for my gear. Some of the reasons why are explained farther ahead. I wasn’t trying to prove how long of a Cat 5e run I could have gotten away with. I really just wanted to see that these Xicom SFP+ modules would actually gracefully degrade to 5gbe.

I was more than a little worried that someone would follow me example, buy these SFP+ modules, then learn that they fool-heartedly attempt to maintain a 10gbe connection even if it was full of errors and retransmissions. I was pleased to learn that they did what they were supposed to do!

The correct way to do this test

I am not prepared to do this the right way because I am pretty sure I left the remainder of my last 1000’ spool of Cat 5e cable at Brian Moses’s house. Even if I still had the spool of cable here, there might not even be enough cable left to successfully break the 10-gigabit connection.

I’d just crimp ends on both sides of the spool and see if adding that length dropped the connection to 5gbe. Then I would cut 10’ or 15’ off the cable, crimp on a new end, and repeat until we see it go back up to 10gbe.

That is about the cleanest way to see exactly how far my setup might be able to go before degrading. I did not do this.

What did I do?!

I grabbed four spare RJ-45 couplers. I collected four spare flat-pack patch cables. I daisy chained them all together, and I put the extra 40’ of cable and couplers in between the switch and the yellow patch cable that connects the 10-gigabit port to the wall.

My iperf3 performance immediately dropped to 4.86 gigabits per second, so I think I did a pretty good job, and I am excited to see that I chose a useful pair of SFP+ modules for this task.

AI Excited guy holding Ethernet cables in his home office

This is just about the worst way you can connect two Ethernet ports. Every RJ-45 connection degrades the signal. The pairs of wires inside the RJ-45 couplers ride along a PCB, those pairs almost definitely aren’t going to be twisted, and who knows if my cheap couplers from Amazon are even any good?!

The fresh 10’ cables are in perfect coils, and the older ones are manually wound up by yours truly. That is absolutely horrible for noise. If we had the gumption to straighten these cables out, then we might be able to go farther before degrading to 5gbe.

What were the results of the test?!

Adding any two of my 10’ cables and couplers to my 70’ of existing wiring had no trouble running at 10gbe. Adding a third cable would drop things to 5gbe, and it would stay at 5gbe with a fourth segment. I doubt I have enough cables and couplers to get the connection to drop any lower, but my suspicion is that it would have drop all the way to 1gbe if it couldn’t connect at 5gbe.

I hope I have already emphasized enough that this is a terrible test of the maximum distance I should be able to get over Cat 5e cable. I am most excited that I finally got to see the Xicom modules connect to each other at 5 gigabits per second.

I bought these modules with the hope that if my wiring would be able to negotiate 5gbe if it couldn’t manage 10gbe, and I was also hoping that would make these inexpensive SFP+ copper modules a good recommendation for other home gamers.

Being able to demonstrate that they worked at full speed over 70’ of old cable was nice, but I feel better being able to tell you that they do indeed degrade to 5gbe just fine!

Conclusion

I think it is best for me to repeat much of what I said in the MokerLink blog post. I don’t think you should be upgrading lots of your home get to 10-gigabit Ethernet unless you are running into a particular bottleneck or have money burning a hole in your pocket.

I absolutely think you should be working on upgrading to 2.5gbe. 2.5-gigabit switches, PCIe cards, and USB dongles are almost as cheap as 1gbe hardware now. Even if you aren’t yet replacing old 1gbe stuff, it is probably time to make sure you’re buying hardware with 2.5-gigabit ports. Eventually your chicken-and-egg problem will work itself out naturally.

While I don’t think you should be upgrading everything to 10 gigabits, I do believe you should be shopping for 2.5-gigabit switches with one or two 10-gigabit ports. Being able to connect my home-office to the opposite side of the house with a fast link is awesome, it didn’t cost all that much, and the reasonably priced Xicom 10-gigabit SFP+ modules should still get you at least a 5-gigabit connection even if your aging wiring can’t manage full speed. That is still a nice upgrade!

Curious about trying out your own setup or have questions? We’d love to see you to join our Discord community. It’s a friendly space where we chat about home networking, servers, 3D printing, and help each other out. Whether you’re just starting or already a pro, there’s a spot for you!

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