In this video, we're going to discuss generic routing, encapsulation tunneling or grid tunneling.
In its most basic form, a GRC tunnel is a point to point tunnel that allows you to transport multiple
higher layer protocols such as IP version four, IP version six, as well as older protocols such as
IP and others across a point to point tunnel.
It's important to remember that GRC does not provide authentication and encryption.
It provides a point to point connection between two routers that emulates or looks like a point to point
tunnel or point to point serial link.
Another advantage of GRC is the support for multicast routing protocols.
In the past, what was often done is that GRC tunnels were encapsulated inside IPsec tunnels for encryption
and authentication.
So GRC would provide a simple point to point link that emulates or looks like a serial link.
But because it provides no encryption and no authentication, that GRC tunnel would then be put inside
an IP tunnel to provide the encryption and authentication.
Now, before going any further, I want to point out that you have access to some features of the VPN
config generator as part of your course.
One of the VPN config generator options is to set up a geo tunnel.
The software allows you very easily to create the configuration required for a point to point Geo Tunnel.
So as an example, by clicking on the show result button, the configuration is automatically generated
for two routers.
He has router two and he has router one.
You could simply copy and paste that configuration into your routers to set up a grid tunnel.
Geary encapsulates other traffic inside a 20 byte IP header and four byte Geary header.
The details of Geary can be found in RF c2784 and as you can see here.
This is for generic routing, encapsulation or GRI.
I won't bore you going through all the details, but if you're interested, have a look at the SA FC.
But notice a payload packet which is the data sent by user.
Pieces would be encapsulated inside a tunnel using a delivery header as well as a header.
In our genius three topology, which I'm going to demonstrate in a moment.
That means that traffic sent from our one acting as PC one to R five, acting as PC two in this topology
is encapsulated by router two.
As mentioned, I'll show you this configuration in a moment and I'll also do Wireshark Captures so that
you can see the packets.
But in brief traffic sent by our one, they sent us normal Ethernet frames across this link, but when
it hits a router two.
It's encapsulated in a tunnel for transmission to router for.
We're going to build a tunnel from our to to our four.
And our three in this case is going to act as an Internet router.
All three is going to forward traffic based on the outer header or delivery header.
Because the tunnel is established from are two to or four or three only sees traffic going from our
two's IP address to our FOE'S IP address.
IT routes based on the order header or delivery header and doesn't look at the traffic that originated
from our one.
Be careful however, Jory doesn't encrypt, so I'm going to demonstrate how you could run Wireshark
on this link and capture the internal traffic that was sent from our one to our five.
So even though you encapsulating the traffic in a tunnel, be aware that that tunnel is not encrypted.
So someone running Wireshark or a hacking tool could see the internal traffic as sent in the payload
packet.
So the original data is encapsulated in a header.
With a delivery header.
The routers on the internet would route traffic based on the delivery header.
When traffic is received by router two, which is the source of the tunnel in this case from router
one, it's encapsulated injury sent across this tunnel two out of four, which encapsulates the traffic
and sends it to a route of five as the original packet, as if this was a point to point link between
route of two and route of four.
Now in this example, I've only got a single router being the internet, but remember, you could have
many, many devices here.
Forming the Internet.
And the idea is that the tunnel is formed from one tunnel end point to another across many devices.
The devices on the internet route based on the outer header router to is an example when receiving traffic
from router, one will encapsulate those packets with injury headers, send it to out of four, router
four will remove the headers and forward the packet across to route of five.
As if there was a point to point the link between router two and router for the same thing will happen
in the reverse.
Router five will send a standard ethernet frame across this link to router for router for will encapsulate
the packet, send it through the tunnel to router two, which will then encapsulate the packet and forward
the packet onto rata one as if there was a point to point serial link between router two and router
four.
As mentioned, I'll demonstrate the setup of this topology and we'll assume that this picture is our
tunnel from router two to router four.
It's simply a session that's established using the protocol from router two to out of four.
But logically, it's as if you've got this extra serial interface.
On the routers, which in our example will configure as tunnel zero.
On both routers.