There are two main types of encapsulation that we'll discuss in this course.
The first one is Hdl-c or high level data link control.
This is a layer two encapsulation once again that can be used across a least line providing layer one
service or connectivity from one site to another.
Now you need to be aware that Cisco have extended the industry standard of version of Hdl-c by adding
an extra field called the type field.
Hdl-c is a very simple encapsulation, and I'll demonstrate a Wireshark capture of the frame in a moment.
But as an example, we have a flag field address, field control field and a frame check sequence field.
Cisco have added a type field to the frame.
So this is different to the ISO industry standard HDL-C Protocol.
Cisco devices do use the Cisco HDL-C or C Hdl-c version by default.
And you'll notice it's very easy to set up a serial link using this encapsulation.
You essentially just have to put an IP address on your router interfaces and no shut the interfaces
to get them to communicate with each other.
If you want to connect Cisco routers to non Cisco routers, you're going to want to change the encapsulation
to PPTP, which is an industry standard version of encapsulation.
Now the reason why Cisco added the proprietary field is to allow multiple high layer protocols to traverse
the link at the same time.
So in other words, if you want to run IP version four and IP version six across a serial link simultaneously,
the routers need a type field to differentiate the frames that belong to IP version four versus the
frames that belong to IP version six when the router receives an IP version for packet across a serial
link.
So in this example, router two receives an IP version for packet from router one.
Router two needs to know that that packet should be processed by the IP version for protocol stack on
the router.
When it receives a IP version six packet, it needs to know that the packet is destined to the IP version
six protocol stack, and that's what the top field provides.
It essentially allows the routers to differentiate between multiple higher layer protocols, and hence
Cisco extended the protocol to allow that functionality.
The industry standard version of Hdl-c doesn't have that type field denoting high layer protocols.
Now it's very simple to configure Hdl-c between two browsers.
You would type as an example on router one, enable confetti interface and the relevant interface.
In this example, serial 1/0, you would configure the IP address on the serial interface.
So IP address 10.1 or 2.1 with the mask 2.5245245252.
As an example, which would be better than slash 24 and then you specify encapsulation hdl-c so it's
as simple as that to configure Hdl-c All you type is encapsulation.
Hdl-c And that is done by default for you.
So you don't actually need to configure that at all.