An open letter to everyone investgating Gigabit switches

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cymon

Limp Gawd
Joined
Apr 16, 2009
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Gigabit switches will still function at Gigabit line-speed even if there is a 10/100 only device connected to the switch. Even if your router is only 10/100, you can still buy a gigabit switch and get Gigabit connectivity. In this situation, attach all Gigabit devices to the Gigabit switch, then connect the Gigabit switch to the router. Gigabit devices are only limited to 10/100 speeds if they are communicating with a 10/100 device.
 
...is this a common misconception? switch != hub, soo the same was (and is) true for 10/100 switches.
 
I personally haven't seen that sort of comment that commonly around here...but I generally don't buy new SOHO routers that often :)
 
It's not extremely common, however I have seen it and I wish to make a valiant effort to fight misinformation of this kind.
 
Why not just point us out to who is saying the opposite instead of posting the obvious?
 
Postcount +1?
But hmmm let's make it more useful.
Gigabit switches that support Jumbo frames must also be connected to Network devices that support jumbo frames. These jumbo frames must be configured to the same frame size on all connected devices/
 
cymon said:
In almost every single thread along the lines of 'Recommend me a good SOHO router', someone will generally say this, for instance, this post ( http://hardforum.com/showpost.php?p=1034542608&postcount=4 ).

Just trying to get the right information out there.
Click to expand...

I think you understood what he said wrong....


He stated "if you need more ports get another switch."

thus meaing that traffic from the switch of the router to the gig switch will of course be limited to 10/100 so if pc1 is in the switch and pc10 is in the router switch he cannot take advantage of the gig speeds....
 
cytech said:
I think you understood what he said wrong....


He stated "if you need more ports get another switch."

thus meaing that traffic from the switch of the router to the gig switch will of course be limited to 10/100 so if pc1 is in the switch and pc10 is in the router switch he cannot take advantage of the gig speeds....
Click to expand...

jchauncey86 said:
Otherwise, just keep the current router and if you need more ports get another switch. Do not get a gigabit switch if you dont upgrade the router as well though since it will be limited to the 100mbps coming off the router.
Click to expand...

Sounds to me like he's saying that you need a gigabit router to take advantage of a gigabit switch.

I hope we all get it now that gigabit connectivity will only be impacted if there's a 10/100Mb link somewhere in between the devices. Two ports on a gigabit switch will still talk to each at gigabit speeds, even if there's a 10/100Mb router in some other port on the switch. If you have a 10/100 switch and a gigabit switch linked together, all traffic passing from the gigabit switch to the 10/100 switch will be limited to 10/100Mb, and therefore all devices on the 10/100 will share a 100Mb connection to the gigabit switch.
 
Well, I have heard some reports that mixed-speed operation suffers in some cheap consumer GigE switches...
 
It is a frequently asked question around many forums. Good information to put out there, but sad it will be lost soon.

And there was a time when I didn't know this, too, but was soon educated on it!
 
Actually, its technically wrong.

There have been several cheaper switches, which I believe are now discontinued, that would drop speed down from 1000mb/s to 100mb/s when a 100mb/s device was connected. These were smaller 5-8port no name switches.
 
Just posted this in another thread, and figured this would be a good place to have it for reference too...

mixedlan.png

(Diagram created with Network Notepad)

In this case, the internet connection (green lightning bolt) would be whatever speed your internet connection is, like 1-10Mb. The green link from the modem to the router would probably be 10Mb or 100Mb, depending on the details of your router's WAN port and your modem's ethernet port. Assuming the router has a 100Mb switch built in, the connection from the router to other devices (the dark gray lines to PC1 and the switch) would be at 100Mb. The light gray connections from PCs 2-4 on the gigabit switch would be at 1000Mb. Just find the slowest link between any two devices, and that will be the speed that they're limited to.

For example, connections from PC4 to PC1 will be limited to 100Mb by the router's switch. If PCs 3 and 4 were both trying to copy files from PC1, they would be sharing the 100Mb link between the switch and router (and also between the router and PC1). Anything going out to the Internet will be limited to your Internet connection speed, as that's the slowest link in the whole network.
 
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