NAT router confusion

Michael H. Semcheski lists at
Thu Jun 23 23:55:52 GMT 2005

On Thursday 23 June 2005 07:43 pm, Ulf Magnusson wrote:
> Is this router really some switch/router hybrid? Or..? Bleh, someone
> please sort this out for me. I realize this isn't strictly
> FreeBSD-related, but I simply couldn't think of a better place to pick
> brains, so I hope I'll be excused :)

It is a switch / router hybrid.  If the traffic is going to an address on the 
same network, its a switch.  If the traffic is going to an address on a 
different network, its a router.

If you understand that concept, then you should have a pretty good idea of how 
the system works.

I do not have a complete enough understanding of IP networks to explain this 
in specific detail.  I think the key is that the computer generating the 
traffic looks at the netmask for the sending interface (eg, 
and uses this to determine if the endpoint of the traffic is on the same 
network or not.  If it is, it sends the traffic directly to the host.  If it 
is on a different network, it forwards the traffic to the gateway address.


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