MTU packets/headers

[Marius Gunnerud]

I thought I knew this but now someone asked me aquestion and disagrees with me so now I am wondering if my info is correct...hehe.

The question was, "does the MTU packet size include the header and trailer?" I would think no it does not, an that it only is calculated from the actual data size in the packet. Is my assumption correct?

Thanks in advance.

[milan.kulik]

Hi,

"By convention the MTU includes the entire IP datagram, including all IP headers, but excludes link encapsulation headers."

See http://www.cisco.com/en/US/products/hw/routers/ps4081/products_tech_note09186a0080094268.shtml

But not all vendors keep this understanding ...

In Microsoft world, e.g., you need to use Ping ... -l 1472 to get the same result as Ping ... size 1500 issued on a Cisco router CLI.

HTH,

Milan