Gigabit Campus Network Design

1) You can have both layer 2 and layer 3 etherchannels. However to answer your question, basically when you bundle two physical paths into one trunk/etherchannel you do exactly that - you make the system see them as one link to the other end. So spanning tree won't take any action. In practice, with decent devices such as Cisco the IOS will take care of all this and you won't have to explicitly disable spanning tree anyway
2) One thing I meant to add but forgot to mention is to keep your structure as flat as possible, i.e. have a 'core' layer of switches then one layer outside these of 'access' switches. Try to avoid having an access switch linked out to another access switch linked out to another access switch if you can. You need to be pragmatic here; if cascading two access switches saves you big money in a corner of your organisation where traffic is expected to be light and there won't be forseeable future growth then I'd do it anyway. But just remember it's not good design

this is some tips that i got from cisco guys :

1- Maximum stacking for access switch is 8 unit but recommended only two unit (24 or 48 port) for 1Gbps uplink

2- If one area have 4 unit access switch, so we need 2 fiber uplink. One uplink for every 2 unit switches.

What is your opinion guys?
Logically, if i got 2 unit 24 port access switch 10/100, the full bandwidth for the switches are ::

24 port switch x 2 unit switch x100Mbps = 4800Mbps

1 uplink fiber SX/LX maximum speed = 1000Mbps

congested is it?

So if we use maximum stack for the switches ::

24 port switch x 8 unit switches x 100Mbps = 19200Mbps
Can 1Gbps uplink support this speed?

The concept of core, distribution and access is not a physical one. First thought that came to mind, what a mess. If you are asking these type of questions, you need to keep your network simple.

hi there..
actually i have 2 questions about Gigabit network.


Situation 1

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From the above diagram, i have fully gigabit device from core switch to access switch using fiber optic for switch uplink and utp cat6 from pc's to switch. If some of the pc's using 10/100 NIC connected to gigabit switch, can it cause a problem to the switch such as speed duplex, packet transfer etc2?


Situation 2

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Is it possible to connect from the core switch to multiple layer of distribution switch such the above diagram? Do there have rules or limitation to extend the network ?

24 port switch x 2 unit switch x100Mbps = 4800Mbps

1 uplink fiber SX/LX maximum speed = 1000Mbps

congested is it?

So if we use maximum stack for the switches ::

24 port switch x 8 unit switches x 100Mbps = 19200Mbps
Can 1Gbps uplink support this speed?

It depends on the utilization. 4800Mbps ya, But as you know thats the maximum, when all 24 ports are heavily send/recieving all the time. which usually does not happen.

So ask your self, depending on the services, servers, net connection, expected user practice. What is the nominal usage rate of a workstation/PC ?

Say for example that most users are expected to connect to the internet , check thier email, ocassionaly download, telnet to an internal server, download/upload files on a file server. So over 1 hour an average user will download/upload say 50MB of data (on the average). Thats less than 1MB per minute X 24 ports = 24 MB /Min which is very low. Your 1Gbps uplink should be more than enough.

However, if the utilization is high, If many users are expected to use say video confrencing, or heavily download/upload larg files more than once a day. If more than 10 users would normally use such bandwidth concurrently so many times a day. That would usually count for a 90% untilization. thats 90% of 100Mbps = 90Mbps. 90Mbps X 2 X 24 ports = 4320MBps, much more than your uplink!!. I would think about spliting into 2 areas and adding uplinks.

However, the 90% case, won't count like this if the downloads or videos are from the internet (say YouTube), and your connection to the internet is say 2Mbps. Obviously, users will not be able to download 90Mbps each no matter how many uplinks you provide!!. It will be much less than that, and there is no point of splitting.

Again, it depends on the "utilization".

I agree with you solo..
it depends on the utilization..

but from my reading / googling on the net, we can't get 100Mbps speed over Ethernet. Theoretically is true but when come to implementation, the actual speed only 45-50%.

What is your opinion?

I'm not sure. may be you are right.

One thing though, the default setting on NICs in Windows is half-duplex. If you set it to full-duplex, it should allow more utilization since it allows your NIC to send/receive simultaneously.