Switch design

Unanswered Question
Mar 17th, 2008

Hi All

Please what is the best way to connect up these switches. There are 2 floors with 3 switches on 1 floor and 1 switch on another floor. Also I want to take fault tolerance into consideration.

Pleae find the diagram attached in visio and gif.


I have this problem too.
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Jon Marshall Mon, 03/17/2008 - 04:52


How many vlans do you have on each floor.

Do you want the 3560 switches on floor 5 do the intervlan routing using HSRP for the vlans ?

A bit more info in what you are trying to achieve will help us give you a better answer.


qwertys21 Mon, 03/17/2008 - 05:14

Thanks Jon.

We have a router which will act as the gateway for the site. Also there is only 1 vlan which at this stage is the default vlan. - vlan 1 on all switches. There are not too many users at this site.

They are all running SMI, so no layer 3.


Jon Marshall Mon, 03/17/2008 - 06:03

If you only want to connect the switches via the gi0/1 and gi0/2 uplinks then you are limited as to what you can do.

Connect 3560 on 3rd floor to 3560 at bottom of your diagram on 5th floor.

Connect 3560 2nd up from bottom to 3560 on bottom.

Connect 2960 on 5th floor to 3560 2nd up from bottom.

Connect router into 3560 at bottom.


qwertys21 Mon, 03/17/2008 - 07:01


I have drawn out the conections suggested. And I have also included mine. Which do u think is ok? DO u think mine will work as well? WIll htere be issues?


jorg.ramakers Mon, 03/17/2008 - 07:52


How many fibers have you available?

Where is the router based?

If the router is based on the floor where the 48 ports is based and you have enough fibers available. You can connect al the lower switches to one fiber port of your 3560-48 switch.

Is your switch has stackwise capabilities? If yes, you can stack your 3560 switches on one floor and connect them to the gig port of the other 3560 switch of the other floor.

Then connect the 2960 via Gig to the 3560 Stack.

I wouldn't connect it like your example. You have to try to limit your spanning-tree domain as short as you can.

If you haven't enough fibers available, try to go for the solution of Jon?

Please don't forget to rate the posts.



qwertys21 Mon, 03/17/2008 - 08:04

Thanks J

They all have fibre ports as they come with SFPs and we can get more if need be.

The router is connected to the WS-C3560-48PS. No, we are not using stackwise technology.

I don't really want to connect all the switches onto one switch.

In Jon's solution, only the bottom 2 switches have redundancy of we loose a link. What will happen if the single link to the 3rd floor is lost?

Wont the spanning tree just block a path and bring it up when a link goes down?


jorg.ramakers Tue, 03/18/2008 - 04:08


I meant the fibers between the building floors. Is it a 6, 12 channel fiber?

If you don't have enough fibers, you have in some place a single point of failure.

In Jon's solution you will give up 1 switch while in your option everything is connected in one line

Spanning-tree will block the redundant links, but you are suggested to use a spanning-tree domain of 7. So on the left side of the root 3 sub switches and the other side 4 switches, otherwise you get spanning-tree delays resulting in flapping links.




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