Number of Cascaded switches.

[Thotsaphon Lueangwattanaphong]

Just a basic question : )

How many Switches can be cascaded in

FastEthernet topology ?

Someone said "unlimited".

Someone said "Should not be more than 8"

Someone said "Must not be more than 2"

What is the correct one ?

Thanks in advance : )

[Georg Pauwen]

Hello,

when you say FastEthernet topology, do you mean that you want to connect the switches using a FastEthernet port, which would result in a daisy-chain configuration like this ?

Switch1 --> FastEthernet --> Switch2 --> FastEthernet ...

In that sort of topology, there is no limit as to the amount of switches.

With Cisco GigaStack, there is a limit of 9 switches, if that is what you are referring to. Can you clarify which switch models you have, and how you want to connect those ?

In case you do want to use GigaStack, have a look at the document below:

Cisco GigaStack GBIC

http://www.cisco.com/en/US/products/hw/modules/ps872/products_data_sheet09186a00800a1789.html

Regards,

GP

[m.mcconnell]

First off, never use the Gigastack GBICs.

STP supports a max diameter of 7 switches, not eight.

Current design practices say you should not cascade more than 2 deep.

-Mark

[craig-allen]

Why shouldn't Gigastack GBICs be used?

[Thotsaphon Lueangwattanaphong]

Yes, What I mean is The switch is connected to each

ohter by Fast/Gigabit Ethernet port ( Not

using GigaStack feature )

According to m.mcconnell's anwer. Seems the

possible number of the switches which can be

cascaded is limited by STP protocol [ Not more

7 ] .But in the real world. We should not cascade

the switch more than 2.

Thanks everyone for the answers.

Happy New Year : )

[Georg Pauwen]

Hello,

if you have just one connection between the switches, you can turn off spanning tree alltogether, hence the STP diameter limit of seven would not apply. Without running STP, there would be no limit, other than the fact that you woudl introduce single points of failure: if one switch fails, everything downstream of that switch will loose connectivity...

Happy New Year to you, too !

GP

[m.mcconnell]

I don't like Gigastack mainly for this reason:

"Using both ports of each GigaStack GBIC, users can implement a half-duplex cascade of up to nine switches. In this configuration, the GigaStack GBIC will create a half-duplex repeater bus external to the switch fabric of connected switches."

Then add this:

"Support for nine switches in a single GigaStack stack offers significant wiring-closet port growth opportunities up to a maximum of 432 10/100 ports per stack."

That is just way too many ports in a half duplex environment. I have had the poor performance of the gigastack kill VoIP - even with fewer than 5 switches in the stack. VoIP likes full duplex and in a half duplex environment there are always collisions - VoIP hates collisions. Other latency sensitive apps are adversely effected as well.

Quotes are from the previously posted link.

-Mark