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We currently in our office have a 20 Mbps fiber optic internet connection with Time Warner. We decided to upgrade our connection to 100Mbps. When the technicians came out, they upgraded the circuit and tested it on their device, but it didn't work on the network. The technicians believed it was because the switch it was connected to wasn't a Gigabit switch. We have a small 5 port switch that we use to connect our data network and our voice network to the internet connection.

While the technicians were incorrect that it wasn't a gigabit switch, that switch in turn does connect to other switches that are only 10/100. This leaves me wondering two things:

1) Even if the switch wasn't a gigabit switch, shouldn't a 10/100 switch be able to negotiate a 100Mbps internet connection? It seems like common sense to me, but I long ago learned that nothing is ever what it seems.

2) Since the first switch is a Gigabit switch, could the other switches on the network being 10/100 cause the connection to fail at that point (rather than just throttling the connection to the maximum speed allowed by that switch.)

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If all the devices connected to your gigabit switch are 10/100, then 100 is the best speed you will get. But you should be able to get that. The gigabit switch should still generally do better than a 100 switch in its place, based on having more capacity internally (so port 1 can do 100 to port 2 while port 3 can also do 100 to port 4, and so on). What model of gigabit switch is not working with the provider device? –  Skaperen Feb 24 '13 at 19:24

3 Answers 3

up vote 3 down vote accepted

Switches normally should be able to negotiate the speed, but those cheap 5 port switches are often pretty unreliable. Consider buying some real hardware that you can configure and where you can set the transfer speed manually.

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+1. SHOULD and DOES is sometimes problematic. If likely works if you force 100mbit on some side. I have seen that failing, sometimes due to cabling, sometimes - due to simply bad hardware. –  TomTom Feb 24 '13 at 18:18

A 10/100 switch should be able to negotiate with Time Warner's hardware.

Most often when I've had problems getting a MAN or fiber internet connection going its been a speed or duplex mismatch between the the Ethernet interfaces.

Try looking at the logs for both the hand off router (if you can reach them) and from the switch on your side (assuming it is managed).

If the auto detection isn't working you should be a le to set both sides to 100 megabiths full duplex and be golden.

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1) theoretically, you are correct. However, without seeing your config or logs, I can't really say where the bottleneck is. A lot of times, the residential based hardware will do the job, but in this case, I believe the techs that came out didn't configure the gateway properly or didn't configure the routes properly. Happens all the time.

2) Networks operate to fit the lowest common denominator. This means, computers connected to a 10/100 switch have a max of 10/100. This is assuming you have the switches and all network appliances set for auto-negotiation. If you have a switch set for half-duplex, then all your devices connected to that switch will run at half-duplex.

Note It's ok that you have 1 gigabit switch in place (I'm assuming you meant to use this like a backbone for your internal network), but your desktops won't be able to fully utilize it unless the other switches connected to it are also gigabit. Also, although you may have your gigabit switch connected in there somewhere, your overall network is controlled by your router, because that's where all your routes are decided. If your router is a 10/100 speed router, then the gigabit switch doesn't help much at all.

Ideally, you should upgrade your router to a gigabit speed business grade router if you want to have any gigabit switches in your environment at all. ZyXel's are very alluring price-wise. SonicWall is also good. There are lots of vendors out there.

After you upgrade your router, upgrade your cheap 10/100 residential grade switches to cheap gigabit residential grade switches. If you don't have a lot of computers, this is fine for cost savings. If you can afford it, your best bet is to drop more lines from the destinations back to the network closet as opposed to using the cheap switches. Network lines are more reliable and less prone to issues, like someone accidentally kicking the switch or unplugging it. Plus, those things aren't built to last forever.

Lastly, unless you have a reason to manually configure your link speeds, don't. This will cause headaches down the line when you run into slowness issues. It's best to let the devices run in auto-negotiate mode.

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