Is it possible?!

[Soon Kwan Kwon]

Hello all,

At first, please show below topology.

"Real topology" is a real situation. 

On the other hand, "GNS" is done by GNS program.

The point what I have a question is why "Real topology" is different from "GNS" situation.

That is, on "Real topology", you can see just one block port,

On the other hand, on "GNS", you can lots of block ports.

Actually, "GNS" topology is the most ideal...

The only thing I set the devices was assigning IP.

The whole mode is L2.

We have no choice but to set the devices to L2 mode.

So, maybe you can tell me changing the mode to L3.

Except for this method, please advise me another method.

I think its problem is STP.(Actually cisco is done STP by default.)

However, I set the machine only IP assignment.

Regards,

[Joseph W. Doherty]

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Posting

Your "real" topology shows as full of L2 loops, so cannot see how that can be "real" and work too well.

Is your "real" only a single VLAN and you are running just the default PVSTP+?

I suspect we're missing some/much information.  Are your "real" and GNS topologies identical, not only in link placements, but link capacies and STP configuration settings?  For example, without setting the STP root switch, it's very likely the two topologies would use a different root.

[Soon Kwan Kwon]

As I mentioned, the only thing I did was assigning IP. 

All of devices are same network.

And STP mode is also same as PVST.

Maybe Root switch is different 

"Real" of Root switch is SG300, whereas GNS is 4500X.

For reference, "Real" is really real situation.

Today I saw it!! Actually I don't believe this situation at first...but real..because switches implement STP by default!