Catalyst 2950

[megatamirul]

How many Catalyst 2950-24 can be stack? What is the maximum number of switch that will work efficiently.

[lgijssel]

This is a figure that you should calculate with a formula like this:

nr of users * bw per user = load. When the load equals 1Gb * 80% or 800Mb in any direction you have the number of users that is acceptable for you. It makes a lot of difference wheter you take 10M or 50M per user.

The 80% is to keep room for background traffic and while you will never be able to load a 1Gb link for 100% over an extended period of time.

For a conservative estimate, take 75%, to stretch the design, you could go with 90%. Then compare the nr of ports divided by 24 and round it up- or down to the nearest full number.

[megatamirul]

Thank you for the advise, but may I know is there any limitation of how many C2950-24 can be stacked?

[lgijssel]

Technically, there is virtually no limit, but ...

The interconnection is done through GBICs, at 1000Mb, half duplex. Stacking five or more will mean that the performance drops. Note that this is not "real" stacking. The interconnection is made through a LAN connection and not over the switch-bus. We never attach more than five on one GBIC uplink. It is sensible to make a calculation as I suggested, while this will give an impression of the load you may expect. It may also give you a good starting point for setting up a well-dimensioned network.

[epylko]

As with most network design questions, the answer is: it depends.

It depends on:

1. What the devices are connecting to. If there is a server that everyone needs to get to, more stacks of less switches will allow better performance (assuming the server can keep up).

On the other hand, if all the devices are contending for internet access via a T1, you can stack as many as you want. You are bandwidth constrained by the T1 and whether you are stacking 10/100/1000 you won't see any difference.

2. If you mean how many can you cluster for use with CMS, the answer is 16. This does not necessarily affect throughput - you can have different switches being managed as a cluster and they are not stacked together.

3. Are you using the stacking GBIC or copper/fiber GBICs? If you use both ports on a stacking GBIC you get half-duplex. The TX (as well as the fiber) GBICs will let you keep full-duplex operation throughout a stack.

Or, are you going to be using the 100Mbps ports? If that's the case I would recommend a hub and spoke design and again ask about your requirements for "efficiently"

4. What your definition of efficient is... high throughput, low delay, no errors.

So, unless you have some performance numbers that you need to meet, I (or anyone else) can't give you an answer that will be guaranteed to work in your situation.

-Eric