[AccessD] OT: Network speeds

jwcolby jwcolby at colbyconsulting.com
Mon Mar 19 13:55:18 CDT 2012


Good article.  but what a PITA that brings up.

I have my WIFI router / cable modem plugging into the gigabit switch *in the middle*.  Does that 
router tell that entire middle switch to dumb down to 100 mbit? if so then there's my answer as to 
"why".  What is left unanswered is how to get around this.  I have lots of internet network traffic 
in the living area at the front of the house, and I also have internet access in my office upstairs. 
  None of it is "optional", i.e. we need internet at both ends of the house for email at the very 
least.  Web browsing as well.

I just crawled under my table up in my office and what I discovered is that the switch under there 
has one line, going to my Virtual Machine Server which shows the gigabit light and the 100 megabit 
light lit.  I unplugged and moved the cable and both lights followed the cable.  I would guess that 
perhaps the 100 mbit is for a virtual machine.

In my server I actually have two NICs and I can assign one of those NICS to support a virtual LAN 
just for the VMs.  However even there those machines have to talk to the internet.

What I discovered is that I have a 100 mbit switch down stairs behind the tv.  It talks almost only 
to the UnRaid server in the basement.  One would expect that each channel would adapt (flow control) 
but the article mentioned the transmitting NIC seems to be the object modified.  What the article 
didn't say was whether the NIC stayed at the lower speed or whether it popped back up to the higher 
rate as soon as possible.

My motherboard in the VM server only has a single NIC so if it is being throttled down and then just 
stays there until a reboot or something...

So much to know, so little time.  And in this case I do not even have the knowledge to troubleshoot 
it effectively.

John W. Colby
Colby Consulting

Reality is what refuses to go away
when you do not believe in it

On 3/19/2012 12:54 PM, Michael Bahr wrote:
> John, for Gigbit to work properly I think **everything** must be Gigibit,
> i.e. all network cards, wifi, routers, switches, etc.  I think Gigibit
> uses jumbo-frames.  Otherwise you can have a mixed-mode condition.  You do
> not mention what kind of router/switch you have,
> consumer/business/enterprize.  Oh forget enterprize--too expensive. :-)
> Some routers/switches may support mixed-mode.  Read the link below.
>
> http://www.smallnetbuilder.com/content/view/30212/54/
>
> Mike...



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