[wplug] Suggestion for discussion

[Brian A. Seklecki]

On Mon, 2010-07-05 at 14:18 -0400, Terence J. Golightly wrote:
> subnet mask to find where network a packet should be routed/nat'd to. 

Hopefully they've explained Class-less v.s. Class-ful networks?

The big question is this:

 - Does the local host, when forwarding a packet to a non-local host,
   need to forward the packet to its default gateway (or other 
   gateway per the routing table / static routes), or does the 
   packet stay within the local LAN (via the directly connected
   interface)

    - Of course, if the destination is on the local subnet, you just
      need to ARP (or whatever L2 protocol discovery for your media),
      and transmit to that MAC/L2 addr.  No router needed.

    - If the destination isn't local:

     -- Back in classful networks, it was easy to figure out based on
        the class of the subnet (1st octet).
     -- Now that classes are gone, you need to compare your 
        interface subnet mask, regardless of the class 
        designation in the 1st octet.


e.g., in 1995, if I was addressed 10.1.2.3, and I wanted to send to
10.4.5.6, i would know that 10.4.5.6 is local, so just ARP and send.

In 2010, if I'm 10.1.1.3 with a subnet mask 255.255.255.248, and I want
to send to 10.1.1.10, I would know to transmit the L3 packet inside a L2
packet with the MAC address of my default gateway (probably 10.1.1.1),
which will forwarded it on appropriately. 

http://digitalfreaks.org/~lavalamp/CIDR.html

I can give you all the CCNA-level training you need.

~BAS (PS, Evo > *)