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RE: 2 interfaces on same subnet

2001-06-05 07:20:03
We CAN have 2 Ethernet interfaces with different IP addresses on the same 
subnet. It's NOT impossible at all. Nothing prevents this.

BUT...

What's the added value? In one of the companies I've been working for, some 
years ago, we had servers configured that way.
Guess what? It didn't bring any added value. Why? Because of the technology at 
that time : old servers, shared Ethernet,...

Let's have a look at the technology.

Outgoing frames will just use one interface. They will not be sent twice on the 
network. So, no added value.
Incoming frames will depend on the kind of network : shared or switched 
Ethernet.

Shared : one frame can travel on the network at a time. So, no added value.
Switched : OK, 2 frames can simultaneously reach the 2 interfaces. So, the 
added value will depend on the server...

Old technology : old server, old processor, old software : no ability to handle 
such traffic. So, no added value.
New technology : new server, new processor, new software : OK, it will be able 
to handle such traffic.

In conclusion : nowadays, it can bring some added value to use 2 interfaces on 
a big strong multi-processor server in a switched fast Ethernet environment.

Hope this answers your question.

E.T.

P.S.: in such a case, DISABLE routing between the 2 interfaces, and do NOT 
install any routing protocol (RIP,...).

-----Original Message-----
From: EXT-Faycal(_dot_)Hadjiat(_at_)nokia(_dot_)com 
[mailto:EXT-Faycal(_dot_)Hadjiat(_at_)nokia(_dot_)com]

Hi all,

I search why we can't have two ethernet interfaces(with different IP address
of course) on the same subnet?
I know it's impossible but why?
Thank you.

BR, Fayçal



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