From: boite-a-spam@plouf.fr.eu.org   
      
   rahul.dev.agg@gmail.com a écrit :   
   >   
   >   I have two linux machines (A and B) connected to same link (ethernet). The   
   MTU supported is 1500.   
   >   
   > If I change the mtu to 1280 of one the host (say B), then can I send an ICMP   
   echo packet from node A (of max size as per its mtu which is 1500) to node B ?   
   >   
   > Will host B be able to receive a packet whose size is greater than its MTU ?   
      
   It depends on B's implementation. Some will, some won't.   
      
   > Is there a way host A can discover the decreased MTU of B and then can send   
   an ICMP packet of lower size ?   
      
   You may try to use a technique similar to path MTU discovery (PMTUD).   
   But it is not the same, as PMTUD relies on intermediate routers sending   
   ICMP "fragmentation needed but don't fragment flag set" error messages.   
   There is no intermediate router between tow hosts on the same link.   
      
   Send ICMP echo packets with the DF (don't fragment) flag set and   
   increasing sizes. If the receiver discards packets bigger than its MTU,   
   of course it won't reply. If it accepts the packet but tries to reply   
   with DF set too, it won't be able to reply. But again, this is   
   implementation dependent.   
      
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