[Gllug] Buying a switch (a sort of repost/recap on an old thread)

[James Hawtin]

On Thu, Feb 11, 2010 at 04:45:26PM +0000, Jasper Wallace wrote:
> On Mon, 8 Feb 2010, James Hawtin wrote:
> 
> > On Mon, Feb 08, 2010 at 01:22:42PM +0000, sean wrote:
> 
> > Don't forget a Gigabit interface is full duplex, so a gigabit of input can
> > be matched with a gigabit output, most peoples use is async in terms of
> > bandwidth so having only on nic isn't really a problem. Current drivers in
> > linux also supports jumbo packets, so you don't have any pesky problems with
> > MTU and it needing to be reduced by 4 bytes to fit the vlan tagging.
> 
> Actually this is a myth - the vlan spec increases the maximum ethernet
> packet size by 4, so the mtu dosn't need change.
> 
> You only need to change it if your trying to send tagged packets to older
> ethernet kit thats dosn't support the spec, but thats very rarely a problem
> since you just send untagged packets to them instead...


Errr I am afraid it isn't, the orginal linux nvidia drivers for my network card
only did packets up to 1500 byte in length. I had to set down the MTU on
other computers to make them talk nicely. Later I got a driver which did
jumbo packets, and everything was fine. Yes the SPEC says ethernet should be
1504 bytes for vlan tagging however that does not mean your card/driver does
what the spec says.

James
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