- [Instructor] All networking is comprised
of several physical devices tied together with cabling.
While the cabling is instrumental,
I'll first talk about the active ethernet equipment.
Modern networks today are built
off of a family of standards known as ethernet.
This standard defines the protocols,
interfaces, cabling types, connectors,
and anything else required to operate a local area network.
I'll begin with the most critical part of any network:
the endpoints.
Networks wouldn't exist if it weren't for client devices
attempting to access resources.
These may consist of PCs, tablets, smartphones,
ATM machines, security cameras,
really anything that happens to connect
to a network and access resources.
At the opposite end of the network lies servers.
These devices hold content or resources
that endpoint devices try and access.
This could be a server storing company files,
email, or streaming video.
Next is the endpoint and server aggregation device:
the network switch.
From small to large, every LAN is built on switches.
Switches generally have between
four and 50 physical ethernet ports
that will cable directly to various endpoints
and network components.
Switches generally operate at the data link layer,
layer two, of the OSI model.
The ethernet standard defines a common header and trailer
used to transmit information
regardless of the physical cable type, copper or fiber,
or the speed of the connection.
It's at this layer that an ethernet frame
is used to encapsulate and send information.
Examine this diagram.
This is a typical LAN sharing information.
Notice how it traverses multiple switches
all using different speeds at different lengths
over differing cable types.
Switches usually have their layer two segments
broken up by a layer three device called a router.
Routers are responsible
for not only network segregation in a LAN
but also connecting the local network
to a wide area network.
A WAN can be any external network resource
like the internet or a leased connection
from a communications carrier between remote offices.
A router will forward traffic from one IP subnet to another.
Examine this diagram.
A small network usually consists of a switch
that connects to a router that provides internet access.
At this point, I will confuse things
by saying that modern switches
often have the ability to perform layer three functions.
These switches are generally referred to
as layer three switches.
One technology that has become essential for many networks
is Wi-Fi, or wireless connectivity.
Wireless clients are connected to a LAN via access points.
Wi-Fi is a layer two technology
that works to some degree like a switch
in that it bridges clients to a single segment
that can later be routed.
An access point is different from a home wireless router.
A true AP doesn't perform any routing functions,
where a home wireless router
will terminate an internet connection
and bridge clients to the LAN.
In smaller networks, each AP can easily be
independently configured and monitored.
In a larger network with 10s to hundreds of APs,
the labor required for even simple changes
across all devices can be time and cost prohibitive.
This is why Cisco developed the Wireless LAN Controller.
This is a centralized management platform
that allows for a single interface
to mass push changes, monitor,
and troubleshoot large wireless networks.
Cisco, like many vendors, are moving to firewalls
that include unified threat management.
Cisco calls them next-generation firewall.
A next-gen firewall allows for not only
standard firewall capabilities to protect the network
but can also perform tasks
like web filtering, inline file scanning,
and perform intrusion prevention services.
Utilizing these tools can help prevent security breaches,
identify compromised machines,
and be alerted to suspicious activity.
Virtually any network can benefit from automation,
especially once the size grows
and/or the demand for network modifications increases.
Cisco's DNA Center is the single pane of glass
that can allow network operators
to manage their network through a centralized dashboard,
deploy devices intuitively using workflows,
and automate provisioning and change management.
DNA provides a means to connect
to a single administration platform
and perform large-scale changes simply.
These basic components are the core
of every network on the planet,
so be sure to understand each intimately.