Subnet and router questions.

[Tommy Hsieh]

Hi,
	We are testing sub-net over here using an isolate small network
which contains 5 machins.  We divide these machines into two groups.
The network structure is something like this.


			(physical ethernet network)
     --------------------------------------------------------------
	|       |       |                       |        |
     ======= ======= =======                 =======  =======
     |  1  | |  2  | |  3  |                 |  4  |  |  5  |
     ======= ======= =======                 =======  =======

	The IP addresses are these :

	1 : 140.75.8.1				4 : 140.75.16.1
	2 : 140.75.8.2				5 : 140.75.16.2
	3 : 140.75.8.3

	The netmask is fffff8 and we use 1 and 4 as routers to route
packets between these two subnets.  All the machines have routed running.
1 and 4 do not have two Ether-Cards.  That means it is still a flat net. 

	The problem we found out is :

	Q) 1 and 4 never broadcast the route information so other machines
	   on their same subnet never pick up the route information.
	   Does this mean the router has to have Ether-Cards ?  What's the
	   requirment to setup a router ?

	Q) Do we have to separate the network like this ?  Add another 
	   Ether-Card to 1 and make it as a router.  Will it broadcast 
	   the route information ?  If yes.  Why ?  Does this means 
	   routed will take a look at how many interfaces the machine
	   has then decides whether it is a router or not ?

	   ---------------------------   -------------------------------
            |            |           |   |          |         |
         =======      =======       =======      =======   =======
	 |  2  |      |  3  |       |  1  |      |  4  |   |  5  |
	 =======      =======       =======      =======   =======

	Any suggestion is very appreciated.


====================================================================
I    Tommy Hsieh              I    Cadence Design System, Inc.     I
I    (408) 944-7869           I    535 River Oak Parkway 	   I
I                             I    San Jose, CA 95134      	   I
I    mail address :                                                I 
I      yhsieh at cadence.com                                          I
I      ...!{versatc,apollo,ucbcad,uunet}!cadence!yhsieh            I
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