ajout IPV4 part 1

07. IPv4 Addressing (Part 1).md

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+---
+id: 07. IPv4 Addressing (Part 1)
+aliases: []
+tags: []
+---
+
+# IPv4 Addressing (Part 1)
+
+## [[OSI Model]]
+
+- Provides connectivity between end hosts on different networks
+(ie. outside of the [[LAN]])
+- Provides logical addressing [[IP addresses]]
+- Provides path selection between source and destination
+- [[Routers]] operate at Layer 3
+
+## IPv4 Header
+
+IP addresses are 32 bits long
+
+Class A
+192.168.1.254/24
+192.168.1. = network portion  (part of the same network)
+254 = host portion (different machine)
+
+Class B
+154.78.111.32/16
+154.78 = network portion
+111.32 = host portion
+
+Class C
+12.128.151.23/8
+12 = network portion
+128.151.23 = host portion
+
+## [[IPV4]] address classes
+
+
+| Class |First octet | numeric range| Prefix Length |
+| ----- | ---------- | --------------|    /8        |
+| A     |0xxxxxxxx | 0-127           |    /16       |
+| B     |10xxxxxxx | 128-191         |    /24       |
+| C     |110xxxxxx | 192-223         |              |
+| D     |1110xxxxx | 224-239         |              |
+| E     |1111xxxxx | 240-255         |              |
+
+
+class D are reserverd for Multicast addresses
+class E are reserved for expermital 
+end of the class A is 126
+127 are reserved for loopback addresses
+
+## Loopback addresses
+
+- Address range 127.0.0.0 - 127.255.255.255
+- Used to test the 'network stack' (think OSI, TCP/IP model) on local device
+
+## Netmask
+
+Class A: /8   255.0.0.0
+Class B: /16  255.255.0.0
+Class C: /24  255.255.255.0
+
+Host portion of the address is all 0's = Network Address
+the netowrk address cannot be assigned to a host
+
+Host portion of the address is all 1's = Broadcast address Address
+The Broadcast address cannot be assigned to a host
+
+## Review
+
+- Network portion / host portion of IPv4 address
+- IPv4 classes
+- Prefix lengths / netmasks
+- Network address / broadcast addresses