the 3 layers

Unanswered Question
Oct 31st, 2007

Hi all, can anyone tell me when people normally use a model with a core switch? If all vlans are routed from the distribution switches, why do they need to have a core ? and also do people use layer 3 in the core or layer 2

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Overall Rating: 3.5 (2 ratings)
guruprasadr Wed, 10/31/2007 - 04:27

HI Carl, [Pls Rate if HELPS]

There are 3 Layers:


1. Edge Layer

2. Distribution Layer

3. Core Layer


Edge layer, where the User / PC / Clients are directly connected. Mostly L2 level operations.


Distribution Layer, where all the Edge Switches are connected. L3 routing takes place and intervlan communication is handled at this layer.


Core Layer, mostly L3 layer were entire campus traffic was routed to Backbone Network / ISP / HO or BO connectivity.

To answer your question, in today's scenario most implementation was handled without distribution layer functionality. Core Layer serves as distribution and core Layer functionality.

80% of traffic in core layer will be based on L3 routing.


Best Regards,

Guru Prasad R

guruprasadr Wed, 10/31/2007 - 05:23


Pls refer the attachment (.jpg) for Modular Campus Network Design.

Server Farm Block:


Any server or application accessed by most of the enterprise users usually already belongs to a server farm. The entire server farm can be identified as its own switch block and given a layer of

access switches uplinked to dual distribution switches (multilayer).

Connect these distribution switches into the core layer with redundant high-speed links.

Individual servers can have single network connections to one of the distribution switches.

However, this presents a single point of failure. If a redundant server is used, it should connect to the alternative distribution switch. A more resilient approach is to give each server dual network

connections, one going to each distribution switch. This is known as dual-homing the servers.

Modular Network Design Examples of enterprise servers include corporate email, intranet services, Enterprise Resource

Planning (ERP) applications, and mainframe systems. Notice that each of these is an internal resource that normally would be located inside a firewall or secured perimeter.


Best Regards,

Guru Prasad R


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