From: gah@ugcs.caltech.edu   
      
   Pascal Hambourg  wrote:   
      
   >> Rick Jones  wrote:   
      
   >>>  All stations in the same broadcast domain MUST have the same MTU.   
      
   (snip, I wrote)   
   >> Is this still true if you have more than one IP net in the same   
   >> broadcast domain?   
      
   > Yes.   
      
   >> I haven't thought of this for some time, but it seems to me that   
   >> you should be able to run separate (sub)nets on the same ethernet,   
      
   > If they share the same ethernet, they are not separate. They are just   
   > different subnets.   
      
   >> with different MTU for the different subnets. You then need a router   
   >> that can route between them.   
      
   > You also need to disable ICMP redirect, otherwise hosts on different   
   > subnets may by-pass the router and start to communicate directly with   
   > each other when they learn the destination is directly reachable.   
      
   Some time ago, I had systems on a two subnet ethernet with the   
   same MTU as part of a network transition. In that case, it was   
   possible to communicate directly. I had an HP-UX machine running   
   gated (instead of routed that most everyone else ran), and gated   
   allows one to configure a metric 0 route.   
      
   In the case of different MTU, it should be possible for smaller   
   MTU hosts to send directly, as long as the large MTU hosts don't   
   try to do it. Also, hosts could have addresses on both nets.   
      
   -- glen   
      
   --- SoupGate-Win32 v1.05   
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