7 switches install in 6 Floor New Building!!

[jolo07310]

We got one 3750 at IDF(basement) and each floor has 3550. They will use GBIC and fiber link connect each other. ALL layer 2.

The questions is what is the best way to do.

I do not want diasy chain together, it is because it will just use one of GBIC at 3750, another link will be used as back up. I want to use both GBIC bandwidth.

So we decide that from 1 st FL to 3 rd FL, chain together and connect to one of the GBICs at 3750.

From 4th FL to 6 th FL, chain together and connect to another GBIC at 3750.

However, we want somewhat of reduadancy, so we want fiber connection between 3 rd FL and 4 th FL. It seems like will create LOOP. What is the command we should put at 3550 at 3 rd FL and 4 th FL to prevent LOOP. I pretty sure use STP, but which comment I should use.

Attached is Visio File, so you guys will understand what I try to say.

Thanks a lot

[smif101]

I would not use that configuration at all, you are building a loop that will pretty much gaurantee you problems. Personally I would have each floor have its own connection to the basement switch. The floors will be your access switches and the basement your distribution.

[jolo07310]

Your solution will be our Ideal. However, 3750 has only 4 GBIC port, there is no way to connect each floor to 3750 at basement.

Thanks

[smif101]

There isn't anything wrong with having a couple of the floors attached via 100M.

[uupsala]

if spanning-tree is working well you will not create a loop. you have nothing to do for this. just cable the switches and power on. for a good traffic-flow on this poor design make the 3750 the root bridge of the tree. the so called backup-link should get a pathcost greater than the summarized cost all other switches to the root. you can edit this parameter in interface mode with #spanning-tree cost xyz. take a value of 2 million if you are not sure what i mean.