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ajout brouillon THhe life of a Packet

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---
id: 1777801183-SYMV
aliases:
- The Life of a Packet
tags: []
---
# The Life of a Packet
## Network Topology
![Diagram](./Images/Diagram_Static_routing.png)
We will follow a packet from PC1 to PC4
mac address for the machine
PC 1 -> 1111
R1 -> G0/2 aaaa -> G0/0 -> bbbb
R2 -> G0/0 cccc -> G0/1 -> dddd
R4 -> G0/0 eeee -> G0/1 -> ffee
PC 4 -> 4444
SRC: 192.168.1.1
DST: 192.168.4.1
PC 1 is in the 192.168.1.0/24 network it need to send the packet in another network
First PC will use An ARP request
it need to find the next interface for the sending the packet
SRC IP: 192.168.1.1
DST IP: 192.168.1.254 -> gateway
DST MAC: ffff.fff.fff -> all of the interface
Src MAC: 1111
ARP request = Broadcast
ARP requply = UNICAST
R1 will answer with an ARP Reply
SRC IP: 192.168.1.254
DST IP: 192.168.1.1 -> PC1
DST MAC: 1111
Src Mac: aaaa
Now PC1 now the Mac address of the default gateway and will encapsulated the packet
with the internet header
+-----------------+--------+
|SRC: 192.168.1.1 |Dst:aaaa|
|DST: 192.168.4.1 |Src:1111|
+-----------------+--------+
R1 Receive the packet and watch the routing table and see
Destination Next Hop
192.168.4.0/24 192.168.12.2
R1 will encapsulated the packet for sending to R2
He will have tot do an ARP request
R2 send a arp reply
Same process as above
+-----------------+--------+
|SRC: 192.168.1.1 |Dst:cccc|
|DST: 192.168.4.1 |Src:bbbb|
+-----------------+--------+
R2 Receive the packet and watch the routing table
R2 will encapsulated the packet for sending to R4
He will have tot do an ARP request
R4 send a arp reply
Same process as above
+-----------------+--------+
|SRC: 192.168.1.1 |Dst:eeee|
|DST: 192.168.4.1 |Src:dddd|
+-----------------+--------+
R4 Receive the packet and watch the routing table
R4 will encapsulated the packet for sending to PC4
He will have tot do an ARP request
PC4 send a arp reply
Same process as above
+-----------------+--------+
|SRC: 192.168.1.1 |Dst:4444|
|DST: 192.168.4.1 |Src:ffee|
+-----------------+--------+