IPv4 Addressing (Part-1)| Day-7

• Routers operate at Layer 3
• PCs connected by switches are part of the same network, sharing the IP address range 192.168.1.0/24
• /24 in the IP address indicates the division between the network and the end hosts
• Routers select the best path to the destination in Layer 3
• Layer 3 characteristics

  1. Provides connectivity between end hosts on different networks, outside of the local area network

  2. Provides logical addressing with IP addresses

  3. Provides path selection between source and destination
• The last number in the IP address represents the end hosts on the network
• If R1 sends a frame to the broadcast MAC address of all Fs

  SW1 will receive the frame and forward it out of all interfaces except the one the frame was received on
• In IP addresses, the router needs an IP address for each network it is connected to
• IPv4 is the version in use in most networks
• Decimal numbers increase by a factor of 10, while hexadecimal numbers increase by a factor of 16
• The /24s at the end of IP addresses are used to tell what part of the address represents the network, and which part represents the end hosts, the PCs
• IP addresses are written using dotted decimal notation
• Each digit in hexadecimal represents a power of 16
• IP, or Internet protocol, is the primary layer 3 protocol in use today
• /24 means that the first 3 groups of numbers represent the network
• R1's G0/0 interface has an IP address of 192.168.1.254, and its G0/1 interface has an IP address of 192.168.2.254
• Binary is used to represent IP addresses, but they are written in dotted decimal for human readability
• IP addresses are 32-bits, or 4 bytes, in length
• Binary is base 2, meaning each digit increases by a factor of 2, it doubles
• Binary 11 10 11 00 is equal to decimal 236
• Binary 10 00 11 11 is equal to decimal 143
• Range of possible numbers that can be represented with 8 binary bits ranges from 0 to 255
• /24 in an IP address means the first 24 bits represent the network portion and the remaining 8 represent the end host
• Remaining 8 bits in an IP address

  Represent the end host
• First 24 bits in an IP address


  Represent the network portion
• IPv4 address is a series of 32 bits, split into 4 octets, written in dotted decimal format for human readability
• Decimal to binary conversion

  Subtract each number from the decimal number starting from the largest power of 2, write 1 if subtraction is possible, 0 if not
• Class C range has a first octet from 192 to 223
• Class A range has a first octet from 0 to 127
• /8 means the first 8 bits are the network portion, and the last 24 bits are the host portion
• Class E addresses are reserved for experimental uses
• Converting 32 binary bits into an IPv4 address

  Divide the 32 bits into 4 octets, convert the octets into dotted decimal
• Loopback addresses range from 127.0.0.0 to 127.255.255.255 and are used to test the network stack of the local device
• Class E range has a first octet from 240 to 255
• IPv4 addresses are split into 5 different classes: A, B, C, D, E
• Class B range has a first octet from 128 to 191
• Class D range has a first octet from 224 to 239
• /16 means the first 16 bits are the network portion, and the last 16 bits are the host portion
• The end of the Class A range is usually considered to be 126, not 127, as 127 range is reserved for loopback addresses
• Class D addresses are reserved for multicast addresses