ARP - Address Resolution Protocol

• Finds the MAC# of another node on local network based on a known IPv4 IP.
• If no response, the gateway router node usually responds.
• Announces change in IP or MAC# to others on local network.
• Checks to see if IP assigned conflicts with another local node.
• Any device on local sub-net may answer query.
• IPv6 uses Neighbor Discovery Protocol
• arp available on most OSes.

RARP - Reverse Address Resolution Protocol

• Provided by a server residing on local sub-net.
• Converts a MAC# to an IPv4 IP.
• Obsolete

BOOTP - bootstrap protocol

• Replaces ARP/RARP
• Server may exist anywhere in domain.
• Listens on port 67
• Replies on port 68
• Superseded by DHCP.

DHCP - dynamic host configuration protocol.

• Server may exist anywhere in domain.
• Provides ARP/RARP functionality.
• Listens on port 67
• Replies on port 68
• Can also provide additional information such as :
  IP of DNS server.
  • subnet mask
  • routers
  • domain-name
  • etc.
  • man dhclient.conf.

MAC# is composed of :

• 3 octet OUI - Organizationally Unique Identifier.
  can be used to ID the manufacturer of the network interface controller.
• 3 octet NIC - Network Interface Controller.
  Unique controller ID
• The OUI/NIC should be an universally unique ID.
• Used at the data-link layer.
• IPv6 does use the MAC for node identification at the IP level on a local network.
  • 64 bit Network Prefix - identifies Domain and sub-net.
  • 64 bit Interface Identifier - generated from MAC#