Use a single smart switch in a network loop?

Posted on 2013-09-13
Medium Priority
Last Modified: 2013-09-18
(Forgive me, our network guys are only here once a month, so we are trying to do some research until then ...)

We have a pretty straightforward network here, but it is spread out over 4 buildings.
We want to make a network "loop", where each building is connected to the next, and then back around.  This is so that if one connection to a building fails, there is a another.

We believe we can do this with only one "smart" switch (located where the servers are), and unmanaged "dumb" switches in the other 3 buildings.  We are told that if the smart switch does "Spanning Tree Protocol", we can set up a loop in this manner.  That switch, we assume, will be a Cisco SG200 model.  

Here's our theory ... network loop diagram
In the example diagram, we would enable port 01 to be active, so all network traffic Building D would go through port 01, through the switches in B and C, then to D.
If the connection between A and B (in red) goes down, then the smart switch would bounce to port 02, and traffic to B would go through D and C.  Does that sound right?

Now, what if the connection between B and C dies ?  Would the Smart Switch (using STP) start allowing traffic through both port 01 and port 02, as the situation would require?

Any suggestions are appreciated.

BTW, Our backup servers are in Building B, in case Building A goes up in flames or something.
Question by:Rob Rudloff
LVL 47

Accepted Solution

Craig Beck earned 1600 total points
ID: 39491647
You've pretty much got it.

The smart switch would block port 1 or port 2.  If the smart switch stops receiving its own BPDUs on the blocked port, that would indicate that the loop isn't in the network anymore (if a link between B and C, or C and D failed), therefore the blocked port would become unblocked and pass traffic.

Assisted Solution

activematx earned 400 total points
ID: 39492018
Yes, very basic and will work with a stp enabled switch.  The cisco SG200 has spanning tree protocol support and you just plug it in, and it will allow the redundant connection without the worry of bridge loops.

Author Closing Comment

by:Rob Rudloff
ID: 39503694
-- thanks!
-- Looks  like we'll be giving this a try in a month.

Featured Post

Get your problem seen by more experts

Be seen. Boost your question’s priority for more expert views and faster solutions

Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

Join & Write a Comment

This article explains the fundamentals of industrial networking which ultimately is the backbone network which is providing communications for process devices like robots and other not so interesting stuff.
This month, Experts Exchange’s free Course of the Month is focused on CompTIA IT Fundamentals.
There's a multitude of different network monitoring solutions out there, and you're probably wondering what makes NetCrunch so special. It's completely agentless, but does let you create an agent, if you desire. It offers powerful scalability …
Michael from AdRem Software explains how to view the most utilized and worst performing nodes in your network, by accessing the Top Charts view in NetCrunch network monitor (https://www.adremsoft.com/). Top Charts is a view in which you can set seve…

597 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question