Author: James Courtier-Dutton Date: To: Hampshire LUG Discussion List Subject: Re: [Hampshire] NAS devices and MTU
2009/12/30 Rob Malpass <lug@???>: > Hi all
>
> Season's greetings.
>
> Can anyone help fill (one of many) gaps in my networking knowhow?
>
> I got a Netgear ReadyNAS Duo for Christmas and performance has been really
> slow. It seems the MTU is the culprit. Two problems:
> 1) Should the MTU on the NAS (I've only ever seen MTU on routers before) be
> set to the same as the MTU on the router?
> 2) It seems the ReadyNAS insists on setting its own MTU as I've told it to
> "Auto-negotiate" the Speed / Duplex mode. The other two options for this
> setting are full or half duplex at 100MBps. I tried both of these
> yesterday which resulted in the ReadyNAS basically dying and only a factory
> reset brought it back so I'm loathe to do it again.
>
> And this brings me to a 3rd question come to think of it....
>
> 3) Is it the MTU that will be affecting performance or is this a red
> herring?
>
MTU is most likely a red herring here.
Regarding the Auto-negotiation.
There is an extra variable to consider.
Modern Ethernet ports contain an auto negotiation of MDX (Crossover
cable or not)
If you switch off Auto negotiation of Speed/Duplex, you also switch off MDX.
This would explain the ReadyNAS dying when you switch to manual full
or half duplex 100Mbps.
If you are using a CAT5 crossover cable, try replacing it with a
straight through cable and visa versa.
As for things to try:
1) Try to determine what the auto-negotiation resulted in each end of
the cable link.
If they turn out to be different, you most likely have a cable problem.
You do not make it clear what devices are on the network and how are
they connected together. Is a network switch involved or not etc.
2) If you are using straight through CAT5 cables, try replacing them
with crossover ones. Again, if I knew how the network was arranged I
could tell you the correct cables to use where.
If one end of the cable thinks it is full duplex, and the other end
things it is half duplex, this could account for your performance
problems.
