Domain names, Domain nameservers, DNS and DHCP are a key part of the internet back bone.

• DNS (Domain Name System) resolves the text domain names to the relevant IP (Internet Protocol) addresses.
• DHCP (Dynamic Host Configuration Protocol) allows the automatic assignment of IP addresses to hardware via a MAC (Medium Access Control) address, sometime domain names are also assigned.
• IPv4 used a broadcast system for ARP (Address Resolution Protocol)
• IPv6 assigns a link-local address to every network interface. It then uses the link local addresses with neighbor discovery for global IP addressing, with a DHCP or Router Advertisements.
• Each hardware connection point has an associated MAC number to which one or more IP addresses can be assigned
  • Unmanaged switches only use tables of the source attached MAC number of the related connected ports for communication.
    • An unmanaged switch does not normally have its own MAC number nor IP address.
    • It builds a table of source MAC numbers for each port, which it change then use for addressing purposes.
    • A port can have multiple source MAC numbers, such when it is attached to another unmanaged switch.
    • An unmanaged switch can not transfer data between VLANs (Virtual Local Area Network). It can transfer data on the same VLAN domain.
  • Managed switches have a MAC number
    • Managed switches usually have an assigned IP address for management access associated with the switch MAC number. (It may be possible that is a separate out of band management port, usually Ethernet, but can be serial port type)
    • Managed switches can be Level 2 only, which allows VLANs to be managed and routed between ports.
    • Managed switches can be Level 3, which allows IP routing as well as VLANs to function. The IP routing functions are often limited, that is not all IP router functions are available on Level 3 switches.
    • The exact management functionality of managed switches varies and not all features maybe available on every model of switch. In fact functionality of managed switches can be expected to vary considerably between models.
• domain names are the text used to identify internet resources. The are registered with a domain name registrar.
• domain nameservers are used to assign IP addresses as well as other information to a domain name.

There are a number of levels of DNS.

1. host file, this is a basic file on each computer where
2. local dns resolver
   1. machine based
   2. LAN based
3. ISP resolver
4. authoritative domain resolver