IPV6/IPV4 Minmium MTU

Why is the minimum MTU of IPV6 (which is 1280 Octets) different to the Min MTU of IPV4 (which is 576 octets) ?Shouldn’t MTU be based on Media type rather than Protocol?

I hope question is clear.

Hi Ruwan,

Those 576 bytes and 1280 bytes you refer to are about the “media type”. That’s the minimum MTU that the router/interface should support.

The minimum MTU of an actual IP packet is much smaller.

According to the RFC, the minimum MTU of IPv4 is 68 bytes:

The header can be up to 60 bytes and the minimum payload is 8 bytes. That’s the actual IP packet.

I think the main reason they increased this is because in reality, every interface supports way more than 576 bytes and it increases the maximum size of the payload, which means less fragmentation.

Hope this helps!