mtu question. more should be better, right?

Mon Nov 7 18:41:32 UTC 2011

On 11/7/11 8:45 AM, Deric Kwok wrote:

> When I setup the server mtu as 9100. why I have to configure the
> switch mtu 9300 to make it working?
> 
> What this extra 200 bytes is for what purpose? ls it standard?

MTUs above 2000 bytes are nonstandard. The most recent Ethernet spec,
802.3-2008, defines a maxBasicFrameSize of 1518 octets and a
maxEnvelopeFrameSize size of 2000 octets to accommodate various encap
mechanisms.

> What is disadvantage of setting our all internal networks (host /
> equipment) mtu more than 1500?

In a single data center at 1-Gbit/s rates or above, probably none,
provided all devices support and use the same MTU. In other scenarios
jumbos can lead to the various problems Iljitsch mentioned.

dn