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Folks,
I was reading
through our most recent OSPF related discussion and the most recent puzzle(by
Howard) brings a couple of questions I had to the list.
Now, coming from a system admin background one of the things I
must note was the ability of the MS windows to immediately identify a machine
with a duplicate IP address within the same network/subnet. The cool thing
here is and maybe you guys can provide some guidance as to how exactly and what
layers of the OSI model plays a part in identifying the duplicate.
When the windows machine is fully booted up and realizes the
duplicate address there is always a notice which also identifies the MAC address
of the other machine using the same IP. This takes us to layer 2 and most
presumably to ARP request from the host trying to identify itself from layer 2
to layer 3. This is a rare thing but windows disables it's NIC card IP
connection until the conflict is resolved. How cool is
that..!
I'm now trying to understand what layer exactly makes windows
disable TCP/IP services. The reason I query is that between a router and a
host on directly connected segment which is misconfigured with an identical IP
addresses, the windows machine will always disable it services and the router
will use the address. This happens even if the machine involved is already
online when the router is booted up.
So my questions and thoughts go to Howard's fendish puzzle in
which case we have 2 router with the same ip assigned. How and why isn't
there some type of mechanism to disable one of the interfaces with the duplicate
IP and where if any notification of the Data Link layer information(MAC
sub-layer) using the same IP on 2 unique MAC addresses. Also, at what layer
would this type of notification be implemented.
Do I have any concept of this reality...
Thought...
Nigel...
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