Network layer delivers packets to receiving hosts.

• Routers look at destination ip address to decide the next hop of routing.

Dynamic Host Configuration Protocol (DHCP)

• DHCP discover looks for the DHCP server.

• After the host finds the server, DHCP responds with offer.

• Host chooses which offer to take, then the host requests IP address.

• DHCP server sends address and ACK message.
  

• 255.255.255.255 broadcasts the message to every host in the same network.

  • The purpose is to let other DHCP servers know the offer decisions so that they can revoke their offers.

• yiaddrr is the IP address the server provides.

• Transaction ID is the ID assigned to the request and the corresponding response.
  

• DHCP can also provide the additional information above.
  

• 0.0.0.0/8 is the default IP address when the host did not receive an address from DHCP.

• 127.0.0.0/8 is a loopback address. The datagram is sent back to the host, making it loopback.

• Private addresses are for the inside network.

• Broadcast address will make every host on the same subnet receive a datagram.

• Hosts within the same subnet can physically reach each other without going through routers.
• Routers are used to reach the hosts outside the subnet.

• Subnet mask tells how many bits are subnet prefixes.
  (alternative to CIDR format.)