Parth-mtu-discovery

Hi,

There is  various mtu configurations(inlc jumbo traffic) for a number of interfaces on the ex switch. But there is also the following statement on the same box...

                         set system internet-options path-mtu-discovery

If junos enables us to configure mtu manually for a number of interfaces, why should this statement be on the same box? Does it make sense?

Thanks

A.