Stacking switches & spanning tree.

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Sep 23rd, 2007
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Hi all,

Id like to consult manner how to connect the switches in LAN together. I know that stacking exists.

But when I need to connect

the switches without stacking and only with the Ethernet cables I ll do this through Gigabit ports and into circle.

So my question is if its good connect all switches into circle? Maybe what is the best solution? And when I connect all the switches together into circle what is the best solution for troubleshooting functionality of spanning tree and all network. Our company is flat. So all the switches are in one server room.



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Edison Ortiz Sun, 09/23/2007 - 10:00
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Instead of connecting the switches in a circular format, I recommend going with a collapsed format.

You would select 2 switches to be the primary root and secondary root of the existing Vlans and connect the leaf switches upstream with their uplink ports.

If you have multiple Vlans, it's often best practice to load balance the Vlans between the 2 designated switches by selecting the odd-numbered Vlans going to one switch and even-numbered Vlans going to the other switch.

How many switches are you planning to deploy and physical location ?

Can you put together a diagram on how your network topology would look like ?


Joseph W. Doherty Sun, 09/23/2007 - 12:14
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". . . what is the best solution?"

"Best" influenced by your requirements and size of topology and sometimes is debatable.

For instance, using a circle or ring connection between your switches is very simple and eliminates a single point of failure. Its major disadvantage is once spanning tree blocks one of the interswitch link connections, traffic that needs to flow between the "top" and "bottom" switches need to transverse all the other switches.

The often preferred topology is a hierarchy of switches in a tree structure. This often provides the least number of transit switches. However, failure of the root switch usually has a greater impact than lost of just one switch in a ring. (One solution to the problem just described, is what Edison is recommending, dual roots.)

For maximum performance, for 4 or more switches and that scales well, a hierarchal structure is best. If minimizing single switch failure impact to your network is important, you could safely just ring connect them for 2 or 3 switches. For 4 or more switches, consider either using the dual root hierarchy or if still relatively few switches, you might channel additional ports within the middle of the logical stack.


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