adding 1G ethernet to a 100M network

[Lennart Sorensen]

On Thu, Jul 29, 2010 at 02:38:49PM -0400, CLIFFORD ILKAY wrote:
> There is a caveat. At a colo facility recently, we installed a gigabit  
> D-Link switch figuring that it would "just work". The network  
> performance of any of the machines connected to that switch was abysmal  
> even though the colo facility had provided us with a 100Gbit/s  
> connection to their Cisco switch. Apparently, consumer grade switches  
> like the D-Link and others cannot auto-negotiate to the highest possible  
> rate if the other end isn't configured to auto-negotiate. The other end  
> was configured to be 100Gbit/s, full-duplex. The D-Link would fall back  
> to 10Mbit/s, half-duplex, thus explaining the poor network performance.  
> Replacing the D-Link with a Cisco (not Linksys) switch and setting it to  
> 100Mbit/s, full-duplex was the solution.

100Gbit/s?  I don't think I believe that.

Now if one end doesn't autonegotiate, then you fall back to half duplex.
You still get the speed right though, but because of colisions (or at
least what the network port thinks are collisions) you get pretty bad
performance.

To me, it is very stupid of the colo facility to not use autonegotiation
by default.  After all if you don't know to set your port to a fixed
setting on your machine, you get the exact same problem.  It is really
just plain dumb of them to do so.

-- 
Len Sorensen
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