08-01-2014 02:56 PM - edited 03-01-2019 07:37 AM
Welcome to the Cisco® Support Community Ask the Expert conversation. This is an opportunity to learn and ask questions about hierarchical network design.
Recommending a network topology is required for meeting a customer's corporate network design needs in their business and technical goals and often consists of many interrelated components. The hierarchical design made this easier like "divide and conquer" the job and develop the design in layers.
Network design experts have developed the hierarchical network design model to help to develop a topology in discrete layers. Each layer can be focused on specific functions, to select the right systems and features for the layer.
A typical hierarchical topology is
Ahmad Manzoor is a Senior Pre-Sales Engineer at AGCN, Pakistan. He has more than 10 years of experience in first-rate management, commercial and technical skills in the field of data communication and services lifecycle—from solution design through sales pitch, designing RFPs, architecture, and solution—all with the goal toward winning projects (creating win/win situations) of obsolete solutions. Ahmad also has vast experience in designing end-to-end data centers, from building infrastructure design to data communication and network Infrastructure design. He has worked for several large companies in Pakistan and United Arab Emirates markets; for example, National Engineer, WATEEN Telecom, Emircom, Infotech, Global Solutions, NETS International, Al-Aberah, and AGCN, also known as Getronics, Pakistan.
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08-01-2014 05:55 PM
How do you maintain a physical three-layer hierarchical network topology with 6807-X/6880-X and the 6800ia?
I mean the chassis is strong enough to be my core. It's got more than enough ports to be the distro. And, since you don't do any configuration to the 6800ia appliance, the chassis now becomes my access port.
08-02-2014 02:14 PM
Dear Leo,
We are discussing the following without any product line, discussing the concept of hierarchical design, which will help you to take decision which model is better for you Two Layer or Three Layer hierarchical model.
Two-Layer Hierarchy
In many networks, you need only two layers to fulfill all of the layer functions—core and aggregation
Only one zone exists within the core, and many zones are in the aggregation layer. Examine each of the layer functions to see where it occurs in a two-layer design:
You can see, then, how dividing the network into layers enables you to make each layer specialized and to hide information between the layers. For instance, the traffic admittance policy implemented along the edge of the aggregation layer is entirely hidden from the network core.
You also use the core/aggregation layer edge to hide information about the topology of routing zones from each other, through summarization. Each zone within the aggregation layer should have minimal routing information, possibly just how to make it to the network core through a default route, and no information about the topology of the network core. At the same time, the zones within the aggregation layer should summarize their reachability information into as few routing advertisements as possible at their edge with the core and hide their topology information from the network core.
Three-Layer Hierarchy
A three-layer hierarchy divides these same responsibilities through zones in three vertical network layers,
At the edge of the access layer, you aggregate traffic in two places: within each access zone and flowing into the distribution layer. In the same way, you aggregate interzone traffic at the distribution layer and traffic leaving the distribution layer toward the network core. The distribution layer and core are ideal places to deploy traffic engineering within a network.
As you can see, the concepts that are applied to two- and three-layer designs are similar, but you have more application points in a three-layer design.
Now the confusion takes place in our minds where do we use Two Layer and where the Three layer hierarchical model.
Now we are discussing that How Many Layers to Use in Network Design?
Which network design is better: two layers or three layers? As with almost all things in network design, it all depends. Examine some of the following factors involved in deciding whether to build a two- or three-layer network:
Again, however, these are simple rules of thumb. No definitive way exists to decide whether a network should have two or three layers. Likewise, you cannot point to a single factor and say, “Because of this, the network we are working on should have three layers instead of two.”
I hope that this helps you to understand the purposes of Two Layer & Three layer Hierarchical Model.
Best regards,
Ahmad Manzoor
08-05-2014 03:58 PM
Hi there -- I was wondering what four types of traffic are you concerned with when considering hierarchical network layers?
THANKS~ sarah
08-09-2014 11:44 AM
Dear Sarah,
My apologies for the late response.
In the network each layer within a hierarchical network design fulfills specific functions.
The functions of a zone are determined by the layer of the zone.
Separating these functions into layers allows you to hide information, a requirement for building hierarchy.
A layer can provide the following functions in a network:
Best regards,
Ahmad Manzoor
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