Question : MTU

I ping a host and it return MTU = 1472, may I know why the MTU size is 1472 but not other size?

Answer : MTU

Because it will be optimum for most of the scenarios of connection. For example your ethernet is capable of carrying 1500 but where it all depends is the connection your have for like Internet. So that is why it is set to be like that.

If you want a generic definition of MTU then have a look at the following link;

http://www.webopedia.com/TERM/M/MTU.html

A more deeper explanation can be obtained at Cisco site.

Cheers,
Rajesh