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IPv4 Header

Unit: 4 Lesson: 1

packets are complicated kinda maybe somewhat

Ethernet only runs at OSI Layer 1 and Layer 2, so it has no idea about logical networking and all the stuff behind that. The Internet Protocol runs in Layer 3, providing logical network addressing and forwarding.

IPv4 Header (size in bits)

  • version - IPv4 vs IPv6 (4)
  • header length (4)
  • Differentiated-Service-Framework - the QoS indicator (8)
  • packet length (16)
  • identification (16)
  • flags & fragment offset (16)
  • source and destination address (32)
  • options and data (32)

Common Protocols

  • ICMP/1 (status messaging; connectivity testing)
  • IGMP/2 (multicasting)
  • GRE/47 (packet tunneling for intermediate networks and VPNs)
  • ESP/50 & AH/51 (used in IPSec)
  • EIGRP/88 && OSPF/89 (remote network info exchange between routers)

#Netplus

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