Hey I'm Clint Garrett Ace Networker and today we're going to talk about the Cisco Hierarchical
Model. Now I'm going to begin this series because we're going to move beyond Network+ because it's
important to you especially whether you have taken the Network+ certification exam and passed it or
not or whether you're still waiting to take it, it doesn't matter because you're going to want
to at some point in your own personal networking career and or business you're going to want to
move forward and Cisco certifications are going to be probably the next logical step for you - CCNA,
CCNP. So you're going to need to understand the Cisco Hierarchical Model but you'll need
to understand it more than for just learning about Cisco products. You'll need to know it
for computer networking in general. We're going to get into Cisco Hierarchical Model, so stay tuned!
To thoroughly understand computer networks whether you're designing them, troubleshooting them,
adding to them or trying to secure them, you need to know about the Cisco Hierarchical Model.
Now we've all dealt with hierarchy and levels of hierarchy in our lives. When we were younger if we
had older siblings we had to deal with the oldest sibling or siblings being favored sometimes more
or with them getting to experience growing up and getting older and being able to do things
before we did. Just as well, to have any civility in a civilized society and any success as a group
of people we have to have different hierarchies to keep things organized and to prevent anarchy
from happening. We have to have law enforcement in case there are those that choose to break the law
and hurt or take from others. We have to have hierarchy within business organizations. If you
want a raise you can't just ask someone lower on the hierarchical level than you, you have to ask a
boss or a supervisor. So hierarchy helps us keep things organized and running efficiently. It's
no different in the computer networking world and Cisco sort of set the standard for how they define
a computer network hierarchy and this hierarchy helps you when you're trying to determine where
you need the most security on a network or where certain devices connect and work the best on
a network. So let's get straight to the Cisco Hierarchical Model. Now the Cisco Hierarchical
Model is more of a logical model than a defined physical layout model. It's a way to logically
define your network or a network to determine where priorities need to be placed again when it
comes to security and certain types of equipment, routers, switches, firewalls, end user devices,
etc. There are 3 layers in the Cisco Hierarchical Model: the Core layer (sometimes called the
"Backbone"), the Distribution layer (also called the "Routing" layer), and the Access layer (or
sometimes called the "Switching" layer). There are different responsibilities you'll find at each
layer of this model and again it's logical and not necessarily physical components. Much like
the OSI Model that has 7 logical layers, there are multiple protocols and sometimes some of those
protocols map to more than one layer of the OSI Model. It's very similar in the Cisco Hierarchical
Model. You may have many devices in one layer and sometimes only one device or single device
in a layer. So before we proceed just remember the definition of the layers is logical and not
physical. the first layer is the Core layer or what many refer to as the "Backbone" of a network.
The Core layer defines the literal core of a network. This is the layer that is responsible
for transporting the majority of the traffic on a network and is the layer whose physical
components are connected to everything peripheral on the network either directly or in most cases
indirectly. The core layer is not only responsible for transporting large amounts of traffic but
transporting that traffic as quickly and reliably as possible. Traffic transported on the Core layer
of a network is common to the majority of users on that network. Now I'll get into this in just
a couple minutes but user data is processed at the Distribution layer and this Core layer gets
the requests forwarded to it by that Distribution layer when they're needed. If the Core layer or
Backbone has any issues with functionality or connectivity, every single user on the network
can be affected. In a majority of cases the Core layer is where you'll implement things like
fault-tolerance. Also since large volumes of traffic are seen at the Core layer, speed and
latency become extremely important here. Again the Core layer gets referred to as the "Backbone" of
a network because it's so vitally important to the life, functionality and efficiency of the computer
network. The second layer is the Distribution layer. It's also called the "Routing" layer
and over the years the Distribution layer has been referred to as the "workgroup" layer. It is
the communication between the Core layer and the Access layer which I'll talk about in just a few
seconds. The Distribution layer provides routing, filtering, WAN access and determines how packets
can access the Core layer if they need to. The Distribution layer has to determine the fastest
way network service requests are handled. After the Distribution layer determines the best path,
it forwards the request to the Core layer, again if it needs to. The Core layer would then forward
the request to the correct service. Most policies are implemented at the Distribution layer. These
are things like routing, access lists, packet filtering, queuing, security and network policies,
address translation and firewalls, redistribution between routing protocols, VLANs and defining
broadcast and multicast domains. And this leads us to the third layer the Access layer. This is
the third layer in the Cisco Hierarchical Model. The Access layer essentially controls the user
and workgroup access to the internet work resources on a computer network. The Access layer
is often referred to as the "Desktop" layer or the "Switching" layer. The network resources most of
the users will need will be available locally on a network and handled by this Access layer but
again the Distribution layer that we just talked about handles any traffic for remote services.
Some of the more common functions you'll see at the Access layer on a computer network are
continued access control and policies, creation of separate collision domains (better known
as "segmentation"), and workgroup connectivity into the Distribution layer. So those are the 3
layers of the Cisco Hierarchical Model, and again you'll need to know this as you progress in your
own networking career and or business in the future. This video and other future videos
is moving toward a CCNA or CCNP certification, obviously because it's more Cisco-focused but
these will be good things to know beyond Network+ level certification and they will in fact help you
on studying for Network+ because if you know these things ahead of time
even before you go in and take your Network+ you're going to be that much more ahead of the
game. So that's the 3 layered Cisco Hierarchical Model and I will see you on the next video!