Now in packet tracer we can see what actual packets look like on PC one PC on the left.
I'm going to start typing to PC two, so I'm going to ping PC two from PC one.
That works.
But what I'll do now is go into simulation mode.
And then I can do the ping again.
Notice the packet is queued on PC one to be sent out of the router.
That's what the packet looks like.
It's got a source IP address of ten 112.
Destination of ten.
One, two, two.
That's correct.
The local IP address of this PC is ten 112.
And we're sending traffic to the remote PC ten.
One, two, two.
I'm going to click capture forward.
Packet is sent to the router.
And this is what the packet looks like on the router.
Inbound PD looks like this or inbound protocol data unit looks like this.
Traffic is coming from PC one, going to PC two.
But on outbound notice.
Source IP address is customer writer one A destination IP address is customer router two.
And on egress or outbound out of the router, we now have a GRC header and a encapsulated IP header.
So the original inbound protocol data unit or inbound information, this IP information is encapsulated
inside an external header.
So going right to the top Ethernet to this is an Ethernet, a link between customer rather one and ISP
one.
External IP header is thus then encapsulated in that we have degree and we have the encapsulated original
IP packet.
Click capture forward.
On this, rather.
Something very similar happens.
Notice inbound Purdue contains the outer headers of customer right of one talking to customer out of
two with the encapsulated original IP packet outbound, something very similar is going to be used,
but what you'll notice is the MAC addresses will change.
So from one interface to another on the router, the source Mac address will change because we're sending
the traffic across a separate Ethernet link when it gets to this router, something very similar.
All that happens here is the Mac addresses are being changed.
The information changes, but we won't worry too much about that.
The big thing to note is the writers are writing based on the external IP headers.
It gets to write a three something very similar inbound.
Purdue still using these IP addresses and so is the outbound Purdue or Protocol Data Unit.
When it gets to this router, however, things change.
So on this router inbound Purdue has the eight network IP addresses and the encapsulated.
IP addresses, but the outbound Purdue has the jury information stripped.
So what you'll notice is inbound.
We have these IP addresses, we have the jury header and we have the internal IP packet information.
But outbound there is no geo re and we don't see Network eight in the list of IP addresses.
The outer headers have been removed from the packet and that's what the client is going to see the client
PC only sees.
The RFC 1918 addresses.
It doesn't see Network eight and these routers on the Internet use Network eight.
So if I go back to say this writer here and look at the packet notice.
Inbound Purdue and outbound Purdue.
Both are using public IP addresses.
But if I go back again to this router, this is where the encapsulation is taking place.
Inbound.
Purdue contains or have seen 1918 addresses outbound.
Purdue has public IP addresses.
A cheery header and the original encapsulated packet.
When we go forward.
To hear.
Packet is DX encapsulated.
So inbound we have IP header duri IP header, but outbound we don't see the public IP addresses.
We don't see the geo headers that's been stripped.
So headers are added here.
Headers are removed here.
So how did you get on?
Were you able to complete the lab?
Did you get your grid tunnel up and running?