identify core switch on my network

First post go easy

i searched the foruum and drew a blank if anyone could point me the right direction i would be grateful:
I'm trying to get my head arounf the concept of the core switch and how to identify it on any given network either via software, or visually.

thanksin advance for any help.

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iowatech

Just double checking here, but are you meaning the router? That's the device that all informationf from 1 site or subnet will travel through to go outside of the local network. To find that just open up a command prompt and type "ipconfig" and read the "Default Gateway" address. This is the case in most simple enviroments, the complex enviroments have multiple routers that all transmit to a router farther down the pipe that takes data completly outside the network to the real internet.

uraken

No my friend i'm happy with what the router is, heres the deal i have a stack of switches in various cabinets across the campus but i often here the term 'core switch' and how it should be top quality and cost a fortune etc so i believe it refers to the bossman switch which all the main cabinets plug into along with router etc etc but i'm not certain.

xwesleyxwillisx

Hopefully we can clear this confusion up. Are you referring to the core switch in terms of STP?

If so, the root switch is based on an election held by all the switches. Once chosen, the switches then determine the lowest cost path to the root switch. The local port with the lowest cost path is known as the root port. Other ports that contain a path to the root switch are disabled by STP, to prevent switching loops. In the event a root port fails, a disabled port will enable for failover.

On the other hand, if you are referring to the "core" layer switch from the hierarchical network model, the core layer switch is whatever you define it to be. According to the model, your core layer switch(s) is/are your backbone of the network. They are low port density and high port speed. No packet manipulation of any kind should take place on these switches. Their sole purpose is to provide a high speed connection to the rest of your network.

So depending on what you meant by core switch, the answer on how to find out is a bit different.

uraken

Posted: Sat Jan 19, 2008 9:46 pm Post subject:

"Hopefully we can clear this confusion up. Are you referring to the core switch in terms of STP?"
No
i'm refering to the core layer switch which acts as the network backbone but how do identify which one it is so i can se if it needs upgrading or whether it is performing ok etc etc.

xwesleyxwillisx

Did you read all of my post?

The core layer switch or switches are whatever you have defined them to be. Typically, however, they would be a 4500, 6500 series switch (assuming you are a Cisco shop).

I guess the easiest way to discover your "core" switch would be to look at your router(s) and see which switch they are connected to.

To be honest though, you may not have a core switch. Depending on the size of your network you may have a collapsed model, where switches belong to multiple layers, i.e. 1 switch has core and distribution layer functions.

For more info on this topic I suggest you read:

http://www.networknewz.com/networknewz-10-20040205UnderstandingNetworkModelsTheCiscoNetworkDesignModel.html

uraken

I read all your article? it was very useful although your second one was exactly what i was looking for and the link was great many thanks and sorry for causing any confusion....

remyforbes777

What brand switches are they? Most vendors usually have a software that maps your network out. That way you can find out where the switches "homerun" into.

uraken

they are all cisco switches 29??

Netstudent

YOu could also use "Show CDP neighbors detail" to map out the switched topology, Ususally the switch that is aggregating all the other switches together will be a distribution or core switch.

Ahriakin

If they are all Ciscos then use CDP as suggested. I havent run it in ages but Cisco have a tool that will map your network based on CDP, very cool and free (also can't remember the name...shoot me I only used it once

). The more R&S'y folks here can probably point you in the right direction.