[TriLUG] Routing...once again.

[Ryan Leathers]

Rick,

the .10, being a host in the 2.2.2.0/24 network, would not be matched by
the routing process, but the 2.2.2 portion of the address would be.  The
packet would be routed out the corresponding interface, and if directly
connected, the layer 2 address of the destination would be retrieved
from cache or ARP.

So, the netstat entry of 2.2.2.0 is showing you the portion of the
address that routing decisions will be based on.  The 2.2.2.10 address
offered in Aaron's example is a valid address in the 2.2.2.0/24 network
which will result in a layer 3 forwarding decision by the Linux host.

Make sense?
  

On Thu, 2006-08-10 at 11:44 -0400, Rick DeNatale wrote:
> On 8/9/06, Aaron S. Joyner <aaron at joyner.ws> wrote:
> 
> > asjoyner at bob:~$ netstat -rn
> > Kernel IP routing table
> > Destination     Gateway         Genmask         Flags   MSS Window  irtt
> > Iface
> > 1.1.1.0         0.0.0.0         255.255.255.0   U         0 0          0
> > eth0
> > 2.2.2.0         0.0.0.0         255.255.255.0   U         0 0          0
> > eth1
> > 0.0.0.0         1.1.1.254       0.0.0.0         UG        0 0          0
> > eth0
> >
> > When you address a packet to 2.2.2.10, that Linux box will look at your
> > routing table, and choose the network with the best match for that
> > packet, which is 1.1.1.0 with a mask of 255.255.255.0.
> 
> Teacher, teacher?
> 
> Did you really mean "which is 2.2.2.0 with a mask of 255.255.255.0"?
> Or am I missing something subtle?
> 
> I know less than enough about network routing to be dangerous.
> 
> -- 
> Rick DeNatale
> 
> IPMS/USA Region 12 Coordinator
> http://ipmsr12.denhaven2.com/
> 
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